Hey, I've got a GREAT GAME!
First, you act like a really awesome big brother and let the little kid hold the hose. Wow, I'm a really great guy for sharing the hose.
Then, you secretly turn off the water, as if by magic.
And then when the little brother gets the hose nice and close to his face to see why the magical stream of water has disappeared, you LET HIM HAVE IT.