Ya know whats the best drink/food to drink/eat during a game?

2. Ya should eat a banana

I would suggest drinking plain simple water and not eat anything during game ( while eating you are not focused on game)

Coffee, tea, yogurt, fruit juice

Pickle juice, seaweed shakes and vegemite sandwiches.

coffee , peanut ,chocolate(non sugar) , highly caffenated soda drinks , tea , honey ,apples and other fruitsetc

all of them increase ur energy especially peanuts or any nuts helps to improve ur brain power

the idea consider caffeinated foods ,good fat rich foods(peanuts,olive oil,ghee, pista,and other nutss)

foods to avoid 

1. milk(makes u sleepy)

2. chips(u loose ur sharpness and shape)

3. all junk foods , throw them out of the window

4.dont eat anything heavy ,always keep it light 

I have played in tournaments while fasting.  Experience has taught me to avoid sugar like the plague.  I have a bullet proof coffee before the round starts, and drink water (electrolytes, magnesium) during play. 

Way back, before becoming a diabetic, I would sometimes nibble on a chocolate bar during games. It seemed to help with my nerves and perk up my attention during play.

#8
Interesting. I used to blunder in the 4th hour of play due to loss of concentration caused by low blood sugar level. The cure I found: drink a coffee with extra sugar in the 4th hour...

Studies have shown that an 8oz. cup of coffee 30 minutes before tests does help.  Sugar is just plain unhealthy.  Sure it gives you that jolt of energy, but then the crash, and all the other stuff it does to your body.  About 112 years ago i was playing in a local weekend tournament.  Some of us were standing around talking, waiting for the first round to start.  In walks these 2 young guys talking about how "epic' last night was, how they didn't get any sleep, and how they were surviving on Red Bulls.  I wanted one of those two in the first round, and i got one!  The poor kid couldn't sit still, knee was bouncing up and down.  So every time he would stand up to go to the bathroom i would move.  This bothered him.  So he sat back down, jittery, and shaky.  He lost, blamed me for playing "unfairly". 

You mention the 4th hour of play?  On time in Reno, two guys in the C section played through all 3 time controls (7 hours).  The next round started, and one of those guys played another 7 hours straight.  14 hours of chess in 1 day.  Needless to say he took a bye in round 3. 

#11
I am not addicted to coffee and usually prefer other drinks like tea for exactly the reason you state: coffee makes nervous.

Yes, sugar is unhealthy. However, after hours of sustained concentration sugar can replenish the energy need of the brain. It is my experience that I blundered less in the 4th hour after coffee with extra sugar.

On playing after fasting: a NM I know could never eat before a competition game as he was too nervous and it affected his stomach. So he always played without any prior meal.

Im thinking of changing my name here from IMBacon to IMCoffee :-)

I have always been a coffee drinker.  Even at a young age.  I pretty much have built up a tolerance to caffeine.  My daily intake is generally 3 cups.  I do love my bullet proof coffees!

As far as energy for that extra push?  My go to is MCT oil for that added kick i need. 

As we are all different no one thing will work for everyone.   But i do think it is common physiology that eating a large meal before playing isn't the best way to go.  It always made me feel sluggish, and i couldn't concentrate.  The first time i tried playing while fasting i was nervous as this was all new to me.  But now...gimme my BPC and im good till lunch. 

I need to lose weight and just somehow cannot eat anything while playing, so it is greatly to my benefit to waste a lot of time playing chess! I do sip water or diet coke, though my best drinks are unsweet tea or diet cran-grape. 

I suppose it is personal presence, but I would say something that isn't to big, etc pasta. Rather I would suggest something like a bar, or energy drink.

#14
So it is a dilemma.
On one side a (heavy) meal before a game makes you sluggish and sugar is known to be unhealthy.
On the other side the brain needs energy like a computer needs electricity and a depleted blood sugar level is known to cause loss of concentration.

On caffeine:
It is known to boost chess performance, but cause nervousness.
"Caffeine – Included in WADA Monitoring Program and relevant for incompetition testing only. Any urine test reading of less than 12 micrograms
per milliliter poses no problem."
https://handbook.fide.com/files/handbook/WADA%20Anti%20Doping.pdf 

On nutrition: here are the FIDE recommendations:
https://handbook.fide.com/files/handbook/Nutrition%20and%20Exercise%20Doc.pdf 

That FIDE nutrition information is virtually identical to what you'll get from any licensed nutritionist. While most of the info is good, some of it is outdated and simply wrong. Unfortunately, nutritionists aren't allowed to think for themselves and are required to regurgitate the official government line.

It states that red meat and saturated fats are bad for you. (The part about trans fats being bad is correct, though.) Those were simply assumptions made without any actual data. Recent studies are indicating that unprocessed red meat and healthy saturated fats are perfectly good for you and don't contribute to cardiovascular disease.

Also, it states that consuming carbohydrates is essential for the human body. That is simply a false statement. There are only a few organs in the human body that need a small amount of glucose, but if you don't eat carbs, your body will make any glucose that it needs via gluconeogenesis. As any person on a ketogenic diet will tell you, your brain functions extremely well when it runs on ketones.

Once starved of carbs, it does take your body a number of days to transition from burning glucose to burning ketones (also known as being fat adapted). During this transitional phase, you will feel like crap. However, once you're ketone adapted, life will be good.

P.S. - My standard keto warning for type 2 diabetics - If you're a type 2 diabetic and want to try keto, you'll probably need to reduce your diabetes meds as you start keto. You should do this under a doctor's supervision, and it should be a doctor who understands keto. Doing it on your own could be very dangerous. (Of course, type 1 diabetes is a completely different issue, since in this case, the pancreas can't produce enough insulin on its own.)

#19
That is all very interesting, but a normal chess player with no diabetes and not on a keto diet needs to supply his brain with energy, so he needs carbohydrates. As you state gluconeogenesis takes a transitional phase of days. You cannot concentrate when hungry or hypoglycaemic.

When i first started on the keto WOE, the first 7 days were tough (sugar withdrawals).  I had sweats, shakes, cramps, couldn't sleep, nightmares.  I woke up on day 8 and felt better than i had ever felt.  My thinking has never been clearer.  If my doctor had his way i would have been on 6 different prescriptions.  None of which would have cured what was wrong with me, but just masked the symptoms.  Through diet, exercise, and prayer i have eliminated or reduced all 6.  I mean im 58....I'm going to have aches and pains. 

Now...as far as what you said about "needs carbohydrates".  Your brain and body will run just fine and even more efficiently on ketones.  So yea...the first 7 days i was on keto i didnt go to the gym for obvious reasons.  Now I go to the gym 5 days a week.  I do cardio 5 days a week and alternate upper/lower body workouts.  I will go after work, and do all this on nothing more than BPC. and a protein bar.  I am a ketone generating/fat burning beast :-)

I have a friend that is diabetic, and me after 4.5 years of keto he still makes fun of it.  He doesnt listen, and tells people that keto is dangerous for diabetics because it leads to ketoacidosis.  He doesn't hear ketosis, no matter how many times i explain it to him.  He gets all excited for Fridays because that is his "cheat day" and he can go home and eat crap he shouldn't be eating, but does because his diabetes doctors says its ok. 

I get its not for everyone, and should not be done without checking with a doctor first.  If your doctor is against keto, then find another doctor.   I have friends that tried and and quit because in their own words: "I'm Mexican i cant give up beans, tortillas, and rice."  While others have thrived on it.  Even eliminating, or reducing prescription meds. 

I usually drink water(nothing else, but i am also not drinking very much liquid because I am concentrating very much). But i think that something like a mountain dew(or a coffee for adults) in a critical moment would be good too.