Here is another wonderful idea from The Toddler Busy Book. My girls have those ride-on toy cars that play irritating music until they get left outside in a downpour. It really was an accident, but I'm not complaining.
Anyway, The Toddler Busy Book suggested having a mini car wash. I sent the girls onto the deck with a bucket of soapy water and a couple of rags. They spent a couple hours detailing their toy cars and not fighting with each other. Priceless!
Their toys get clean, they get clean. It's a win-win situation!