What You Should and Shouldn't Put In Your Mouth Before Performing
Just to clarify: Nothing that you eat or drink can possibly have any direct effect on the quality of your voice. When you swallow, the food goes down your esophagus, and never comes in contact with your vocal cords. The following may effect other aspects of your performance (ie. breathing) but not the vibration of the vocal folds.
Good
1) Water -- in moderation. Remember that saliva is your mouth's natural lubricant, not water. If your mouth is dry from nervousness (not thirst) chew gum to keep it moist. Just remember to spit it out before you go on stage.
2) Citrus juice -- (you should water it down to avoid the "lumpy" feeling that it can cause in your throat)
3) Mints and mint flavored things -- if you must have tea, this is the way to go!
Bad
1) Milk products -- the lactose coats both throat and stomach and may effect your breathing.
2) Carbonated beverages -- burping mishaps
3) Sugary foods
4) Coffee -- you're just asking for mucus buildup
Anything can damage your performance if you consume too much. Singing and dancing suffer the most from overeating -- a full stomach puts pressure on the diaphragm and prevents you from breathing properly, and can cause cramps. Whenever possible, eat at least a few hours before performing to give your body time to digest.
Take a straw for drinks backstage so you won't mess up your makeup.
Remember that everyone is different. While some people maintain
that lemonade is great before a performance, others have found
that it gives them a lump in their throat if they don't water
it down first. Experiment with different things until you find
what works best for you. Then let us know!
_______________________________