Can I put vinegar in toilet tank to get rid of mold?
Here is an article that might help - https://blackmoldcontrol.com/how-to-remove-black-mold-from-your-toilet-bowl-tank-and-seat/
You can use vinegar. I have recently used the Lysol toilet cleaner in the black squirt bottle and it removed some stains I had tried to get out for over a year.
You can use the vinegar along with a scrub brush to help loosen and remove the mold... but you may also need a stronger chemical to remove it if you are unable to scrub certain areas.
If you have a newer toilet or newer toilet flushing mechanism, check the owners manual. Ours is very specific about what one can use without damaging it. I would probably use hydrogen peroxide and elbow grease so the solution doesn’t sit in there very long.