C. I can’t imagine devoting more than a few seconds’ thought to something like this. “Oh, hey, someone brushes their teeth at work. Huh.” If it was still there the next day, I might escalate to option A. Maybe.
Actually, I’m enough of a lazy slacker that I’d probably just let it sit there indefinitely. It’s someone else’s toothbrush, so what do I care?
I can assure you that if I ever saw toothpaste and a brush above the sink in a service provider’s bathroom I would sack them immediately. There is no way that I would allow something like that to go unpunished. Minor considerations like price and service just fade into obscurity when faced with the slap in the face that is toothpaste and a brush in a bathroom.
Do I know them? I mean some people are on a payback list don’t ya know.
Likely I’d leave it. A few days later it would disappear, because I know that nobody would use it after sitting in a certain bathroom a couple days. The sink is 12 inches from the urinal and gets splashed. Maybe things are different for the OP’s bathroom.
C at 9am; A to the address specific to our floor at 3:30.
The thing is, the company brags on endlessly about how our center is “World Class”, and we’re on the high end of the price range. We get prospective new customers coming in on tours, and a toothbrush in the bathroom might make a difference to them.
We work in a small office in a big office building. We share the toilets with the entire floor. I would have no idea whose toothbrush and stuff were in there, and it would be just as likely to come from some other office. C, no matter when I see it. Not my problem, none of my business.
Since the stuff was left on a counter above the sinks, what’s the big deal with just doing nothing? It’s not preventing anyone else from using the sinks. Sending out an email can be outright embarrassing. Tossing the stuff is rude. Cleaning the toothbrush has to be a joke. Maybe leave things as is, and if it’s offensive to your eyes, drop a paper towel over it.
Totally C. I like to be thought of as the person around the office who’s a good choice for projects involving creativity and organizational skills, not the person with good attention to detail for the finer points of office housekeeping. That said, for the type of facility **blondebear ** is describing, I think management would appreciate that attention to detail.
Monday morning - it is still there. So I pissed on it.
Well, it’s still there, and apparently someone came up with a response I had not thought of. Someone taped to the shelf a little cartoon image of a person, with the words "Please rinse brush after using. Thank you."
Bwahahaha! 
A splash of hot sauce may be appropriate next time.
It is gone!
(but the little cartoon remains.)
I don’t know about ABCD, but it’s an office, not a college dorm. At work I don’t want to see evidence of other people’s grooming habits strewn around. If you brush your teeth, trim your nails, pick your nose at work, OK, just keep it to yourself. Don’t leave your crap laying around in space used by others.
B. It’s a health and safety violation.
For a toothbrush? C. No contest.
If it were a ring, watch, something valuable I’d drop it off with the admin assistant and A.
C. Unless by some chance I thought I knew who it belonged to, then I’d ask them. Otherwise, no, they’ll figure it out sooner or later.