But I did a little experimenting when my 5 year old neighbor threw out a broken swimming pool toy that shoots water. I cut a hole in the bottle's lid so that the toy fit in snuggly and covered with duct tape to avoid any leaks. I don't give this one to people who like to shake it around forcefully.
I originally thought I might have people pull the long handle up and down as a fun way of doing exercises. But then a staff person suggested using it as a ring stack. This made perfect sense since it can function as an adjustable ring stack. It is now being used with a lady who has a spastic right hand that she can wrap around the handle while stacking rings with her very functional left hand. I love that we can adjust the height of this ring stack according to who is using it.
I have not been able to find the exact same water blaster toy on Amazon but these look like they might work.... Since I work with adults, I would try to remove or cover up any childish characters.