Kids spilled a Wendy's frosty in the back seat and I didn't know about it for a few days so the cloth was hard and stained. I mixed warm water with a little bit of laundry detergent and scrubbed with a brush I use to clean my shoes. Have a towel ready to wipe up the soapy lather that forms after you scrub. Dip in the solution and scrub for a bit until you're satisfied. It got the Frosty stain out and the area where it was spilled was no longer hard and crusty.