Use a mixture of soap, borax and hot water cleaner. To make another natural, non-caustic cleaner, grate a bar of soap until you have 6 tablespoons worth.
Add this and 2 tablespoons of borax to a bucket. Slowly add 2 cups of boiling water. You can also add 10 drops of lavender essential oil for fragrance if you want. Allow this to cool and then whip it with a whisk until it is foamy.
Brush the foam onto your upholstery with a soft-bristled brush. Rinse the area with warm water by using a clean rag. Rinse out the rag frequently.
Work on one seat or area at a time. Rinse each area thoroughly before moving onto the next area.