Dos and Don'ts of Food
Alcohol
Elvis never drank alcohol. Alcohol affects your ability to sing well. You should not drink at all if you want to sing at a professional level and if you do, then definitely don't drink on the day, or even the day before a performance. If you did drink some alcohol, exercise it out of your system as soon as you can and drink a lot of water.
The Don'ts
Don't drink alcohol, citric juices like oranges (acid reflux), milk (flehm), no chocolate, no hot sauce, no fizzy drinks like Coke or Pepsi.