This is so MPSIMS-ish that I’m not going to put it in GQ - there is now a fresh (human) urine stain in my car. (smartCar, for what it’s worth.)
If I don’t get rid of it, what’s the worst that could happen? (Other than odor) does it do something corrosive to the cushion underneath?
Google said use some dish detergent, but I don’t like the idea of detergent being left on the seat either.
It’s fabric upholstery, not leather or plastic.
Baking soda any good?
My guessstimate is that almost half an ounce went into the car seat.
I would get something meant for cleaning pet urine, because they’re widely available and will probably work.
Yes, the pet urine sprays should stop any smell from the surface, alternatively bicarb or white vinegar, but to get it out and clean it properly, take it to a car detailer’s and have them use their steam cleaner on it.
Ok thanks…how does the seat cushion (polyurethane? i don’t know what these cushions are made of) interact with things like urine, baking soda, spray, vinegar in general?
I’d suggest a local car wash place or an auto detail shop. I assume they’ve seen and smelled all sorts of spills, stains and so forth, including a variety of bodily fluids.
Although in this case, we’re told it’s only half an ounce. That’s so little that I’d try to address the problem myself before spending the money on hiring someone. Something like Febreze might help.
I can’t tell you, I’m no expert. In my experience, bicarb won’t hurt the fabric (it won’t get through to the underneath). White vinegar in solution, ditto. Nature’s Miracle site for cat urine products says you can use them on fabrics and furniture, so probably no issue using those (not sure how cat urine compares to human).
The main thing is to get the urine OUT of the cushion (or as much as you can). You need the sucking from the commercial steam cleaners to do that. Most other remedies are more for the surface of the upholstery.
I second this. Just take it to the detailer. They will know what to do, and if you don’t do anything, beyond cleaning up the visible mess, they won’t have to undo whatever you did.
Pet urine spray, yes. And use a wet vacuum first on the urine and then on each application of the spray. The later applications of the spray should be allowed to soak a while to give their enzymes time enough to break down the proteins in the urine. The final vacuuming should be done for a long time, several minutes. After the last liquid comes out, you still want to evaporate whatever remains.
Steam clean the seat, and never again pick up a hitchhiker.
The next time a passenger says (s)he REALLY has to pee, listen! 
So, how’s Popi doing these days?
Can we get the backstory on this, please?
It’s going to hurt your Uber reviews.