All you need is two sponges, two bowls of similar size, a measuring cup and water. Super easy and frugal.
Fill your bowl about half full of water with the measuring cup (we used 6 cups).
Take your bowls and sponges outside and space the bowls your chosen distance apart.
Have your kids soak the sponge in the water and then run to the other bowl as fast as they can. Have them squeeze out the sponge into the empty bowl. Repeat until the first bowl is empty!
Last, measure the remaining water in the second bowl. We ended up with only 2 cups of water! You can make it a little lesson by showing them how the water was lost by dripping, etc (cause and effect) and by subtracting the water you ended with from the water you began with (math concept).
Of course, the kiddos got a little silly at the end. Anyway, enjoy!