Gertie LOVES to play with an empty water bottle. Here in Az. we have too many of them laying around. So I put a little water in a couple and laid them on their side and put them in the freezer. Once frozen I put just a little bit more water in them and gave them to her. She had a BLAST! She loves to roll them around on the floor, or out on the patio and they're nice and cool for her to play with and chew on. They don't stay frozen very long in this heat, so I filled one up and froze it and it stayed cool a lot longer, but the bottle wasn't quite so "crackly" and she likes the crackly bottle. If she chews til there's a hole, I just toss it in the trash, as there are plenty more where that one came from. She prefers this to any of her store-bought toys, just like little kids who would rather play with a box!