Not hard, but fun to do. Good visuals for spectators.

Fill a ~ gallon can full of water. Lid on or off. If on, just set it on top, don't seal.

Place an empty can smaller can (ie 12-20+ oz size) on top.

First person shoots gallon can (bottom) with "high powered" cartridge from about 50 feet away. (We've done it with 222 rem, 30-30, 308-probably a good 357 mag/44 mag HP will do well too).

It bursts and sprays, sending the smaller empty can skyward.

A second shooter pops the flying empty can with a shotgun-and sends it flying sideways.

Fun and easy.