I installed a bicycle valve in the cap of a 2 liter bottle, pumped it up to 100 PSI, and then
burst the bottles by shooting an arrow through them with my
home made crossbow.
For added effect I filled the pop bottles with wood shavings. That way, there were lots of visible bits thrown around.
Simple water bottle rocket
I drilled a small 3/16 (4.5 mm) hole in the cap of a pop bottle. With the bottle filled half way with water, I
inserted the compressor nozzle in the bottle, pumped it up, and let it go.
There isn't much in the way of directional stability to this thing. Fins would help, but that would be more work
and add weight to the thing which would make it not go quite as wild.