> Doing magic with sodium polyacrylate
> LINK · 'The Disappearing Water Magic Trick' on The Spruce Crafts
On a recent episode of Bob's Burgers, a character mentions a trick using something that's used in diapers.
For the curious, it's sodium polyacrylate, a largely-harmless compound that is ultra-absorbent and can make water solidify almost instantly. It's very cheap to purchase and a fun trick to do (when it goes right).
This page on The Spruce Crafts gives more detail.