In serious tournaments, I never drink beer while I'm still in an event. However, once eliminated, I have had moments where I had to follow the walls back to the room.
LOL!
What's a serious tournament? Anywhere you had to travel from your regular venue? I don't drink too many beers myself, but I'm lucky I guess to have the control to keep it to a beer an hour while in an event, and actually look for those Monster or Red Bulls, juices and espressos (most places have excellent coladitas and coladas down here in SoFlo). And water or sodas are always available, but I hate those.
In a non-serious setting, it's not unusual to have 2-3 beers.(about my limit) I certainly don't think it helps my game. I'm far too relaxed to begin with and have a hard enough time focusing without drinking.
I actually have quite a few friends whom I've played with for over a decade, and without that beer keeping them in some sort of "zone," their play can be erratic. Have competitive pool and darts buddies that exhibit the same beer=oil need. It's when they stay idle too long and the beer or drinks pile up, that's when they lose the edge. But they still do better than staying dry, and they certainly don't get along, are tense, and more excitable when they're staying dry. It must make a difference with the tolerance each player has, and if he or she's used to the beer being present, the lack of it can have really bad consequences: arguments, disillusionment with the partner, etc...