Best Toilet cleaner especially for hard water stains. For a clean toilet without a lot of fuss, just pour a couple cups of vinegar into the toilet before bed, swish it with a toilet brush in the morning, and flush. This simple strategy will sanitize your toilet and remove those stubborn hard water stains too. Why This Works: The acetic acid in vinegar kills viruses, germs, bacteria & mold. It also dissolves tough mineral deposits and stains.