You will be able to hit people just with a water bottle cap! If you do it right it can kind of hurt. Sorry but I dont have a camera, and I dont have enough money to buy a camera. Infact I dont have my own car.
Step 1: Basics
You can take a 1pt,0.9 fl oz bottle, and be able to hit someone with the cap because of pressure build up. You should use a dry bottle, but you can ad water in it and it will be more powerful.
Step 2: Getting Ready
You take your empty or filled bottle, and have the cap on. (if your filling it only fill a little bit). Gentley unsrew it abit. Have it so you can easly unsrew it, but so no air or water can get out.
Step 3: Loading
Twist the bottom as tight as you can, and then your bottle is loaded. Or you can lay it on the ground and step on the bottom of the bottle, and when it is flat roll the bottom up.
Step 4: Fire
Now your done. All you do now is ame then use your thumb to twist off the cap, and...BOOM! It makes a loud bang and if you aded water and it was tighten good you can see evaorated water coming out!