Not to worry.... I always squeeze the extra air out of the bottle before I cap it!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
Make sure you tell them it's for GAS not NITRO FUEL. I don't know if it's all gas proof.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.