We have these also with popcorn and water. You can make one with just popcorn and little items. There is one pictured of beads and a block. And the last one is a magnetic one.
If you have nothing else you can put paper clips and I attach a magnetic want to the bottle and the children like to see the magnet move the items inside.
I also like to use things attracted to magnets that things that don't. Then they learn about what items magnets attract.