I don't use sweeteners either. Sucralose is claimed to be safe, but then again its a chlorocarbon, and the liver generally does not like those. It is heat-stable however, and one of the more popular sweeteners.
People have had some negative results with stevia. I think heat decomposes it and the products are not tasty. Too big a molecule to purposely inhale in my opinion.
Some use ethyl maltol (cotton candy flavor) or one of the bavarian cream flavors, or a touch of vanilla.