If you take your dog along on car trips, even just brief trips to the store, eventually your car may develop a dog odour. While your dog won't mind if your car gets a bit smelly, you and your passengers probably will mind. Musty dog odours can linger a long time if you don't do something about it. You don't have to clean your car upholstery and carpet completely to get this smell out, although that would help. You can get rid of the musty dog odour quickly and inexpensively using just a few products.
Mix white vinegar and water, half and half, in a spray bottle. Spray a small section of fabric upholstery to check that the vinegar and water mix won't fade the fabric.
Spray this over all the car upholstery and carpet. Spray extra in the area your dog usually is held (the back seat, for example).
Wipe down all upholstery with a soft cloth, if the upholstery is leather or vinyl. Otherwise, just roll down the windows and let the fabric air dry.
Sprinkle baking soda over the carpet and upholstery, as suggested by carspace.com. Leave it on overnight and vacuum it up in the morning. Most of the odour, if not all, should be gone by now.
Spray the car interior with a commercial odour-neutralising spray. Many brands exist, and offer many scents.
Instead of spraying vinegar and water, you can soak a piece of bread in vinegar and place it on a saucer in your car overnight, as suggested by rd.com. If upholstery needs cleaning anyway, and you have time, go ahead and use a carpet and upholstery shampoo on your car's interior. Brush it in and vacuum it up later when it has dried. Then use the vinegar spray or a commercial odour neutraliser for additional freshness. Another home product that removes some odours is old coffee grounds--just place them in an open container and leave it in your car overnight (don't pour them on upholstery or carpet directly as coffee can stain). Your car will smell like coffee, but this is usually a more pleasant odour than dog.