You have been given some very bad advice from some untrained singers apparently.
First, using your voice as little as possible is not the way to become a better singer. The vocal cords are muscles and, like any muscle, need to be exercised and trained. Granted you don't train for a marathon by going out and running 25 miles the first day, but you don't train for one by sitting on the couch watching TV either. The voice needs to be trained by using proper singing technique, keeping the muscles in the neck and throat loose, keeping the larynx low, breathing properly and not stretching and straining to sing outside your range. And people who quote "you need to sing from your diaphragm" know absolutely nothing about singing.
As for what to drink, water is best. Keep yourself hydrated. Lemon is a horrible suggestion because it is acidic and will dry out your vocal cords (any citrus is bad that way). Same with caffeine (coffee, tea, soda) or alcohol. Those things are fine to drink, but not before you need to sing for any length of time. Also, you shouldn't take antihistamines before singing (also dry out the cords).
I would advise you to not take advise from this site. Go find a good vocal coach and get your advise on singing from an expert.