My sister in law, Jenny, makes the best sensory tubs! Every time we are at her house she has something new and fun for her boys to play with in their tub. I really need to get better at changing up my sensory tub options, because sensory tubs are one of my kids' favorite activities!
This tub is filled with popcorn (I like to buy popcorn in bulk at our local Winco, which has a huge bulk section). Then, she added farm toys. A barn, animals, tractor toys, and little people.
Popcorn gets EVERYWHERE. I find the easiest place for clean-up of popcorn related activities is the carpet. It just seems easier for me to "scoop" it up when the kids are finished. While you can sweep hard floors, they popcorn likes to roll around easily and seems to spread out all over the floor. At least with the carpet it doesn't roll away ;)