Too much water at once can be a bad thing, too. Your kidneys may not be able to handle large quantities. I recommend drinking half of your body weight in ounces over the course of the day, every day. This helps keep your stress levels down. You'll also be more focused, alert and it will help you remember things.
Also, stay away from cough drops or anything mentholated, they will strip your vocal chords.
Get plenty of sleep and when you can avoid talking. If you have to talk a lot through out the day make sure you have proper breath support.
Currently~ Miss Myrna Thorn in Ruthless! the Musical
Recently~ Emma Carew (Jekyll & Hyde), Sister Mary Leo (Nunsense), Demeter (Cats), Tzeitel (Fiddler on the Roof)