Hope this helps:
Hi Suzie, this may help you. https://www.hometalk.com/1836913/toilets-why-clean-the-tank
Here's what Bob Vila does, or at least says he does:
Have not heard from you in quite awhile. You doing ok?
Pour in some "The Works" toilet bowl cleaner from the Dollar Stores. Let sit for a few hours then flush. It removes rust stains and built up crud so well you will be in for a surprise with no work other than lifting the lid.
depends how gross it is ;blue can easy off oven cleaner works great!!! ---yep cleaned some really gross places. Iron out or straight white vinegar for any left over rust stains or good ole Comet cleanser green scrubber and elbow grease; adding white vinegar( 1-2cups) to toilet tank and bowl let sit over night for help with mineral deposits in bowl & tank will reduce ring build up where bateria for mineral build up
Easy ways to clean the toilet tank
Cut off the water supply and drain. Scrub the interior with white cleaning vinegar. You might want to let it sit for a white before flushing it out. Then turn the water back on and flush.