I have a great tea that I have developed through trial and error. It works really well for keeping the voice lubed and warming it up.
Dave Heagle's Tea recipe:
any de-caf tea will work
1 tea bag,8-10 0z. of hot water, let steep
1 teaspoon of slippery elm bark powder
1 teaspoon of honey
mix very throughly and repeat mixing periodically, it tends to settle in the bottom and needs a quick jazzin up.
I prefer mine really hot but be careful that you don't go overboard and burn yourself.I usually drink 1 full container before a gig and keep warm water handy throughout the performance.
Slippery elm affects everyone differently so do your research before using this mixture. You will most notably notice a difference in your bowel movements,so go easy till you determine what your body can handle.