DIYs often get a bad rap for being too difficult or complicated, such as the ubiquitous Pinterest fails — great in the photos, not so much in execution. But DIY water-balloon piñatas are different.

Piñatas are often the centerpiece at parties, birthdays, and quinciñeras. Put a partygoer in a blindfold, spin them around, and let them swing a bat at the piñata hanging above. Can they crack it open ...