This one takes a little nerve…
Practice Nosework in a full parking lot.
I don’t recommend putting odor on a stranger’s car. That, to me, is crossing a line. But, why not take a moment and run your dog through a quick search of cars without odor?
The goal would be to work the space, maybe a whole row of vehicles. You know there’s nothing to be found, so you can get your dog working quickly, along the outer edges or even running blank searches in squares around the cars.
If you’re going to search blank, simply work your dog along a row and then at the very end of the search, reward the dog for their search. We generally don’t reward dogs for searching when there isn’t odor, but if the dog does a full search and finds nothing they might become frustrated, so you want to reward them at some point.
Another option is placing odor on your car in the middle of a row of cars without odor. That gives the dog a reward opportunity, while still searching many blank vehicles.
Of course, the possibility is that someone will approach you and ask what you’re doing. I’ve found being honest works best. Generally, people are interested in dog training.
I’ve only done this a few times, and I chose a park and ride lot because I assumed that the car owners wouldn’t be anywhere in the vicinity.
Of course, if you work in a place with a full parking lot, you could certainly ask your co-workers if they minded if you ran some nosework searches with your dog in the lot. If they’re your co-workers, they’ve been hearing about nosework for a while and it would be a chance to give them a little sample (and to have them meet your dog).
Be creative, but be safe!