If you've ever had milk spilled in your car, and it soaked in before you could clean it up, you've discovered that it is absolutely THE WORST smell known to man.
Your car becomes unusable. You have to ride with the windows down no matter the weather. And the hotter it is the worse it gets.
When my son spilled some milk on a trip and I didn't know it, I discovered the smell two days later. I had to leave the windows down all the time when it was parked. At one point the smell was so bad that i could smell it as I approached the car...from 10 feet away!
I searched for answers. Carpet cleaner - nope. Vinegar - nope. Baking soda - nope.
I only found two things that worked...one that covered the smell and one that got rid of it.
I sprinkled fresh coffee grounds (not used yet) onto the carpet in the areas where the spill was, and rubbed them into the carpet. That effectively masked the smell, and made my car smell like a Starbuck's! And while it did seem to absorb some of the smell and covered it pretty well, I still wanted the base odor gone for good.
I finally discovered that PetZyme works! I bought a spray bottle of it from a local pet store and saturated the area where the milk had spilled. I did not blot it, per the directions. I just let it soak up and absorb and evaporate as needed. It really was pretty amazing. I guess the enzymes/bacteria in Petzyme break down whatever the odor-producing bacteria are from sour milk.
I understand there are two types of PetZyme and that one is more 'perfumy'. I stuck with the plain one.
I hope you find it works for you!