There was a very cool long post here.. about the differences of comic timing that is based on food, liquids, and any substance we put in our bodies before a show that will directly relate to our memories, timing, and even energy.
Water- No affect on timing, probably helps memory, definitely helps you pee faster, or sooner, and then... keeps you hydrated so you sweat like meatloaf. And if you are biting it on stage, you can always say, "gee I forgot to hit the head" which is also a funny line and truth.
Milk, Juice, or other benign beverage, (not soda)- Okay, you're putting some sort of incremental mineral, or vitamin in your system which may or may not affect your synapses. You may feel fuller, and sated. Digestion will put your body in a restful state, unless your lactose intolerant, then the IBS fairy lands squarely upon you and you'll be squeezing that charmin in no time. You'll add liquids which keep you quenched, but you may find that some of these have sugars that slow down your response time. Sugar is great in chocolate, and bad in comedy. Unless it's pie. Then it's great.
Coffee, Tea, and Me. I mean, Yeah, you know what I'm saying. Coffee is a natural way of dehydrating you. If you've been hard pressed to use the lavatory, wolf down at least 6 ounces of coffee or tea, which stimulates the prostate in men and the bowel in women. It's nature's Drano. It also takes all the spongy cells filled with body-helping water and makes them like grapes turning to raisins. More caffeiene, more inner rainsins. If you have something salty with that caffeine, your body not only decides to squish those cells into pressed raisins, but then with salt, the water that manages to set out of those cells is now running in and out of veins and muscles. So you get bloated. Coffee- dehydrates you and makes you swell. Lovely. Bad for the blood pressure, bad for the stress of your heart, and really bad for trying to fit a ring onto your hand.
Thin women tell me- I'm going to hit the gym right before working out so I'll be skinnier on stage. They're not really understanding the chemicals of muscle. When we work out, our muscles absorb as much water from our system as they can so they can heal better, and quicker. As a result, there is a bit of swelling, and they tend to weigh MORE after a work out than they do at any other time. If you want to look thinner after a work out- then hit the gym a full day before you're needed on stage. Otherwise, wear baggy clothes.
Beer on stage- everyone drinks beer on stage, right? That does wonders for comic timing and great audience interaction. Well, not really. What it does is puts you in a state of not clearly knowing what your words are, and when they have arrived to teh mic. It also makes it look like you're afraid of the audience. Very few people pull off drinking on stage as something cool, or part of the act. One person, Steve Seagren, aka CopScotch, has alcoholism as part of his act, so having the prop of the liquid works very well for him. A friend puts tap water in a beer bottle when he does shows in front of college kids- it makes him look like "one of them" but then he is very sober and his act is just filled with great timing.
Drinking as habit, drugs before a show. You may think you have it covered, and that no one can tell the difference but I can list at least 80 comics from about 300 that are not rehired for gigs because of this. It starts with a "can I bring a beer on stage?" and the whole act is completed, as written, without much ado. Then they'll have a beer before the act, the one during. Then two before, two during and one after. Then the progression goes crazy and it seems to start the Wednesday before, and end six weeks into the future. People who use this as their way to perform don't have very long careers. They offer to do gigs for free-- and people know they get what they paid for. The bad part is, generally there is a measure of good comedy in these guys- but they don't have enough confidence.
The best chemicals you can put into your show- endorphins and adrenaline. Laughter kicks in both for me.. and excitement begets excitement. Keeping your ears alert, and pushing for material that spawns better laughs, always works to bring out the chemicals of laughter and comedy.