Why do they only seem to drink water at chess tournaments?

It's easier to drink something when you're getting paid to do it. :)

There's not enough money on the world to make me drinking that crap.

I've never tried it. I doubt that I will.

Coffee during, beer after for me. :)

I too notice that the frequency of visits to facilities (to "pass water") during a chess tournament is at least double or triple the normal rate.  Even if I forget to drink enough water.  I believe (as a chemist) that this reults from the unusually high brain metabolism during a tournament.  The waste products of biological metabolism are mainly carbon dioxide and water.  And an active brain burns through a lot of calories, especially when under the stress of a tough chess game.

You could replace the content of the container with whichever beverage you prefer and profit. Casi no puedo creer ya no lo has descubrido este truco simple. 

Googling: "how to disinfect a can".

my coach says only to take occasional sips of water relaxingly to intimidate other player

but i would prefer chocolatte milkshake 

alas!. I'ts not allowed

Could be vodka.

c'mon, we all know it's vodka!

Alekhine had milk, Short and Kamsk had orange juice (which, if i remember correctly, was the basis of a fun prank the former pulled off on the latter where he stuck a label reading "poison" on the orange juice carton)🤣

I have blue bull at tourneys, that probably explains my low rating. 😁😁🍺🍻🍵☕🍷🍸🍾🥂🥛🥛

Alekhine's milk glass at the far end

I bet there is!

HA HA, a woman I work with (about 3 years now) said to me recently, "I've never seen you drink water." About the only things I drink are coffee and beer. Somehow I survive.

I always drink water because drinking water helps your brain function better, and sugar makes it go way worse. In fact, I've seen people at my school have one sugar item and lose all the rest of their games from a great winning streak.

I saw some people having a banana or an apple on the table.

Carlsen stopped drinking orange juice because it gave him sugar highs. Just like any fruit juice, OJ is high in sugar (or more specifically fructose). No one would think of consuming 15 oranges or 30 apples during the course of a game. But 1 litre of fruit juice or, even worse, coca-cola or other fizzy drinks, many seem to do without as much as batting an eyelid. Personally I prefer water and coffee.

As for the reason we go to the toilet/bathroom so often during the game, isn't that simply caused by the nervous tension? When I was in my teens, I used to get headaches after the game, due to the high tension.