There are two effective methods to repair cigarette burns on car upholstery. Coit's carpet-cleaning, spot-removal guide shares one method that uses mayonnaise and one that uses super glue plus small fabric fibers.
In the first method, Coit suggests taking a little mayonnaise and rubbing it on top of the burn hole. Allow the mayonnaise to soak in for a few minutes, and then wash it off using water and a soft cloth. The mayonnaise should clear up any marks left by the burn, but if there are any burn marks left, use a small knife to scrape them off. Next, using a small razor, cut off a piece of matching upholstery from a not easily visible area on the bottom of the car seats. Make sure the fabric matches the pattern of the burned area being covered. Using fabric glue, take the cut piece of fabric and attach it to the burned area, completely covering it.
For the second method, take a razor blade and gently scrape the seats until bits of fabric and lint start to gather. Keep these bits handy. Next, squeeze a small amount of super glue into the burned area. Place the fabric fibers on top of the super glue. After the glue is dry, the glued fabric should blend in well with the rest of the upholstery.