If you need to clean the tank, you can cut off the water supply and empty. Then fill with white cleaning vinegar. Let sit for a while. Then turn the water back on and flush until all the vinegar has left the tank.
Or dump a large amount of water in the bowl so it flushes itself and then pour it into the tank.
Here's a youtube video on how much to use etc
These are 50+ uses for vinegar that you can use in your home.
PS - We have a FREE eBook with recipes for all of my homemade and all-natural cleaners. You can download it here --> https://pinkfortitude.com/thank#GreenClean
It depends on what’s dirty in the tank? Mold? If there’s corroded metal parts, the acid in the vinegar will make them worse.