Oh, for heaven's sake! Why be so inventive when you don't need to? There is ONE thing that makes many, many cars smell just awful. It used to make virtually ALL cars smell awful, but now probably about half of them. Maybe even less than half.

Cigarettes.

It's that simple.

Yes, there are other things that can add to the rotten, stinking residue inside a car, many other things, but the number one and worst of them will always be the enduring aftereffect of a few thousand butts smoked in a small enclosed place and reeking forever and ever in the stinkin' ashtrays. Every now and then, the ashtrays start to overflow. Then the person who drives the car dumps the whole friggin' mess all over some grocery store parking lot and starts over again. It's a lovely sight, almost as lovely as the smell inside the car.

If it's revenge you want, though, you need a quick fix. I think the cat urine already suggested above is the A-bomb of bad smell quick fixes. It's so damned hard to eradicate.