One of my daughter's favorite activities in her sensory bin is dry beans! We picked up a set of cheap cup-measure scoops, then we grab a plastic bowl out of the cupboard and let her go at it. It takes maybe 30 seconds to set up and a minute or two to clean up, depending on where all the beads get to. When she's in a particularly messy mood (aka I don't feel like vacuuming the carpet to pick up missed beans), I just put down a tarp. Much easier to pick up that way. I just heard about this one by word of mouth, so I don't have anyone to link for it.
Using her shovel to put the beans into the bowl
Swishing the beans around the bin
Lots of fun! I set this up a lot when I need to get a chore done, or get dinner going. It's great :)