Air

• Air out the car. You can plug an extension cord into a fan and place it in front of an opened door. If you can keep your doors opened throughout the night in the garage, the air will help remove the odors of the car.
  
  

Baking Soda

• Sprinkle baking soda throughout the stained areas of the car. Baking soda is sodium bicarbonate, which neutralizes the acidity level of stains like urine and vomit. When baking soda is applied to an area, it is able to absorb the smell. Allow the baking soda to sit on top of the stain overnight, then vacuum it up in the morning.
  
  

Urine Remover

• There are a wide variety of urine-removing products on the market. Urine-removing products contain enzymes and bacteria that eat through urine crystals. Even though you may not see the urine stains, the acid from the urine is deeply embedded in the upholstery fiber. To find out where the urine is still lurking in the car, use a handheld black light. Place the car in a garage and turn out the lights or use the black light at night. Run the light over the upholstery. The urine will look green underneath the light. Spray the stained area with the urine-removing product and do not blot. Allow the product to eat through the urine. Repeat this step if the smell of pet urine is still evident.
  
  

Shampoo

• Vacuum the entire car before shampooing. Take the seats out of the car with an Allen wrench if the pet odor is coming from underneath the seat. Fill a bucket with 1 gallon of water. Spray the stained area with shampoo. Dip a sponge into the water and squeeze, then rub the stained area with the sponge. When bubbles start to form, wipe them off with a towel. Use fresh water and a clean sponge for rinsing off the stain. Leave the windows rolled down overnight to help the stain thoroughly dry.
  
  

Fabric Refresher

• With a wide selection of fabric refreshers on the market, it can be hard to choose the right brand. Pick one that has a scent that appeals to you and is specifically formulated to cover up pet odors. While the refresher will make your car's upholstery smell better, it will have to be reapplied because it only covers up the smell--it does not neutralize the acid.