Plastic water bottle caps are more than just a massive strain on the environment. They can also be used to perform this cool party trick! All you do is hold the cap in your fist and then pound said fist from the bottom with your other hand. If you do it right, the cap should launch high into the air with a nice little pop. This is sure to impress the guests at your next party or puncture the cornea of one of your enemies, depending on what you aim the cap at.