What to drink during OTB-Tournaments

Water and coconut juice.

I drink mostly tea, or some kind of fruit juice

I think I will try tea, and guess there are different teas, with and without coffeine

A question that makes me think HARD!

Right before i play i will have a cup of coffee.  Studies show that a small amount of caffeine before mental exercise will improve your score.  While i play a lot of water, and trips to the bathroom.

Bourbon.

In 7 rounds 3 day fide classic tournament i make sure i sleep and eat well 3 days before tournament. Then 1.5L orange juice plus few banannas with solid meal somewhere and energy drink should be enough for intensive 3 days for me.  And some nuts here and there for the brain and chocolate or coffee at morning. It's importhant not to be distracted with anything for example in middle of the game you start to worry about some other stuff.. 

water or soda but that could mess up your thinking

I've seen a study that suggests drinking coffee in the morning (at certain times - to do with body clock) doesn't improve alertness so I would avoid it during a morning OTB game. However, coffee works very well for me in an afternoon tournament game or a midweek evening league match.

Yaeger Bomb.  Yeagermeister  with beer chaser.  Or Boilermaker