You don't want it to explode. Make sure it has a way to relieve excess pressure. A soda bottle may eventually burst and make a good day real bad quickly.
IMHO
At your local hobby shop they should have a fuel bottle made for the little rc gas cars. It is a plastic squeeze bottle with an aluminum spout and rubber cap. I always ride with a camel back type back pack and I put this bottle in there in the upright position.