A wet spot, if left alone, can produce an unsightly stain on upholstery. Pesky round rings left after an area has been wet are known as water spots or water rings. The rings are minerals and debris in the fabric which is pulled to the outer section of the spill while the fabric is wet. Removing these stains can be time consuming but possible with the right set of chemistry.
Blot while the fabric is still wet from the original spill. Even if the spill is nothing more than water, continue blotting until you can't pull anymore liquid onto the cloth. The less moisture left in the fabric, the better the chances of not creating a water ring when it dries.
Dampen a towel with white distilled vinegar. Test it in an inconspicuous area of the fabric as you would with any cleaner. Check for color loss, shrinkage or other fabric damage before proceeding.
Apply the vinegar to the stain by lightly dabbing with the towel. Do not rub because this can cause fabric distortion. Work from the outside of the stain to the middle to keep the water ring from spreading.
Allow it to sit for several minutes. Blot to remove the vinegar.
Rinse the area with clear water. Do not pour water onto the upholstery. Either lightly mist the area with a spray bottle, or dampen a towel with clear water and dab the area in the same manner as you did with the vinegar. Blot the area dry with clean towels. Repeat until the water ring is no longer visible.