or look for silver caps on top
poke it with a stick
boom
What about plastic bags?
Those won't gain enough pressure, they will just do 'pop'
sounds like funI'll have to try it
A buddy of mine made one with toilet bowl cleaner and it's a pretty damn loud boom but if you really want a nice boom you can always create a propane bomb, just keep in mind that creating this variant of bottle bomb is a felony and don't do stupid stuff like stand over it when it's about to go off if you value your skin.
This how Boston was attacked?