I don't drink, but definitely do not have a night on the town the night before. LOL. Someone from my school went to a tournament a few years ago and basically went out to the bars the night before. Slept the whole tournament up in the bleachers until it was his turn to perform. Even then, he was pale faced, nearly threw up several times, and needed alot of water. Won like a good place in forms, 1st or 2nd, and like 2nd or 3rd in sparring. Maybe the Drunken Master Technique works for some people, but I don't care to try it. LOL
Another thing, don't eat alot of sugar and stuff that will make you sleepy. I ate Pizza at the last tournament for Lunch and I was fine, but then again I've always had a stomach of iron. I can't really say, other than keep away from stuff that makes you sleepy, or might upset your stomach. Maybe eat some veggies, rice, fish or chicken, and somejuice and plenty of water the night or even the day before. Eat some yogurt cereal or high energy foods in the morning. Eggs, Bacon, Toast, Milk(not too much) and high protein stuff. I always get sleepy sitting around at tournaments if I don't get plenty of rest and eat a hearty breakfast in the morning because my tournaments aren't til late in the afternoon. Just don't stuff yourself. Maybe eat some small energy bars or the yogurt from breakfast, and snack on energy bars and drink plenty of water throughout the day before your match. Just not like right before your match, or you will hurl.
Hope some of that helps.