The writer and director of The Sandlot, David Mickey Evans, posted these pictures of The Beast on his blog with the caption:

I had several "GIANT THE BEAST PUPPETS" built for the movie. One was a completely articulated "Giant The Beast Head" and another was a full over-sized "Giant The Beast Puppet Suit" brought to life by two brave puppeteers actually inside the suit.

They were designed and built by my friend and puppeteer genius Rick Lazarini.