We had a large collection of big car wash sponges of different kinds with several big buckets of soapy water. They then drove them through the spray of the hose to rinse them off.
This activity bubbled off (couldn't resist) to some children washing the playground equipment and getting buckets of water to rinse it off themselves.
Since they enjoyed this activity so much, we wanted to give them other things to wash. In order to get washed something has to be dirty.....
so we made dinosaurs dirty by painting them lots of beautiful colors..... then washing them in our water tables.
Another day, we spent the early part of the morning painting the tires on our playground....and then washing them off.
These washing activities may seem pointless to an adult, but to a child they are meaningful. They like the cause and effect of making something dirty, clean...and something clean, dirty again. Washing is something they see the adults in their lives do, so this kind of play let's them try those roles on and feel independent and confident. They also gain a lot of pleasure from the sensory-ness of the activity. The feeling of the soapy water, the squishy sponges and the splashing. It allows children of many different ages and developmental levels to experience the same activity together but within their own abilities.
Now if I could just have this much fun doing laundry!!