My sister helped me make a Lego brick pinata for William's 6th birthday party. We made it using a very large cereal box, gorilla tape, plastic cups, tissue paper, and hot glue. Here's how we did it:
Fill box with candy.
Cut holes in the top so that you can later hang the pinata.
Reinforce the top with lots of Gorilla tape.
Cover with tissue paper.
Cut the bottoms off of plastic cups, cover in tissue paper, hot glue onto box.
The Finished Lego Pinata!
Tie a rope or string through the top, hang it up, and let the children have fun breaking it open! When we made this pinata we cut holes in the sides of the cardboard box to make sure that it would be weak enough to be broken open by the children. In the end, however, that wasn't necessary. Eventually the bottom of the pinata opened up because the weight of the candy became too much. It lasted the perfect amount of time, though. Each of the 14 children each had two turns to hit the pinata before the bottom dropped out.