Piñatas are three-in-one fun: wild excitement for the kids, entertainment for the adults who are watching, and a package for party favors.

The only negative is all that candy! Here are some non-candy filler ideas.
Non-candy treats for a piñata
Retro toys such as trolls

Pens, pencils, and pencil sharpeners

Balls, such as super bounce balls

Tattoos

Small toys such as cars

Mini flashlights

Bath bombs

String bracelets

Which would you scramble for?

I also sometimes match the treats to the piñata design. For example for a “ball” party, we had a ball piñata full of balls (golf balls, super bounce balls, etc.). For a back-to-school party, we had an apple pinata filled with apple-related treats and school supplies.
