Does anyone use a plastic carbonator cap with a bottle smaller than a 1 or 2 liter plastic soda bottle? I have a 1 L soda bottle and it works just fine. I bought a 500 ml Pepsi bottle and no matter what I do, the cap doesn't make an air tight seal. I have some 12 oz bottle of home brew that's undercarbed so I was looking for a smaller bottle to try to add some carbonation to it.