15 tips for cleaning in your car including: For general carpet or upholstery stains, take a gallon of hot water, a generous amount of dish detergent, and add a cup of white vinegar. You'll need a hard bristle brush to work the mixture thoroughly into the carpet fibers. Let sit for 30 minutes. Blot until dry with towels or thick absorbent rags. (This also works well for pet stains).