I just bought some litter box cleaning wipes at Petsmart, just in case the Lysol wipes I had been using weren't safe. These are pet safe and I had a coupon so I thought I'd give them a try.
I use "clorox anywhere" on all my kids things, my dogs things, and will probably use it on Pumpkins things as well.
Spray it on and let it dry-it's a very weak bleach solution.
I usually use bleach and hot water, but now I think I'm going to try dish soap and vinegar. I always worry that I don't rinse the boxes enough when I use bleach.