Just googled this (some are more relevant than other):
Another problem many presenters have is the dreaded dry mouth syndrome. At one time or another it hits most speakers. No one is immune. In order to avoid and cure this problem, before making a presentation, consider the following seven guidelines:
Watch the foods you eat. Avoid caffeine, sugar, chocolate and dairy products. These items can make you thirsty and parched or create mucus.
Use Vaseline on your teeth. This helps your upper lip slide over the teeth and create saliva.
Bite the tip of your tongue. Don't bite so hard that it draws blood, just enough to create saliva (hey, that's pretty kewl!).
Drink plenty of water. Make sure it's room temperature or warm -- not ice-cold. Consider adding a wedge of lemon -- it can cut the phlegm, but may be too acidic for some stomachs.
Stop smoking and avoid alcoholic drinks. Both of these vices are hard on the throat.
Watch what you wear. Your clothing should be loose around the waist to help you breathe better and around the neck so it doesn't choke you.
Sit up straight! Your mother was right. Good posture while speaking can help your voice stay healthy.
<edit>guess i was wrong on the whole candy thing, sorry!</edit>