There are products at the pet store that work well. Just look for a Enzymatic Pet Stain AndPet Odor Remover. There are several brands and most pet stores have their own brand which is cheaper thanname brands.
You can also use coffee grounds. Take the wet grounds and put them on a plate and close the windows and leave in the car. I have used this method with other odors like spilled milk and it worked.
I have heard that charcoal also absorbs odors but I have not used that method.
We own a pet care service and believe me I have dealt with a lot of pet issues. We couldn’t go without the enzyme cleaner.