Keep him warm. You can put a heating pad under half the cage, or cover one end of the cage with a towel and shine a lamp on it so the heat goes into the cage. Make sure the lamp is not so close that it could set the towel on fire. You only heat half the cage so he can move to the other side if he gets too warm.
Providing electrolytes is very beneficial. If you have Pedialyte or a sports drink like Gatorade you can give them that to drink, or you can make your own using this simple recipe:
http://www.webmd.com/hw-popup/rehydrati ... ar=hw86827A small amount of cayenne pepper sprinkled in the food may or may not be helpful. It won't do any harm anyway.