Clean old Pet Carpet Stains. Pour enough vinegar to soak the stain and THEN add a small amount of baking soda. If you do the reverse, you will have a noisy, bubbly mess. Do it the right way, and you can hear the recipe cackling away, telling you how it is cleaning and deodorizing without leaving any residue. You need to let the spot dry for a day or two before sweeping up and then vacuuming.