I hear alot about limon-water, hot-tea, olive-oil, and all these kinds of things to drink. What works the best when you have 4 hours of singing to do and you want to be able to still hit the notes during the last song?
I've done a bit of work 'providing' for singers (see 'best job' thread). Many of them ask for a jug of still water with a few slices of lime in it. Lime's better than lemon, apparently. They don't drink ice-cold water, either - contracts the vocal chords.
Stay away from tea, coffee, red wine and anything that might have tannin in it - that's also bad for the voice.