Use white vinegar, baking soda, and Coke to remove tough stains. To dissolve mineral buildup, rust, and grime, combine the power of Coke, vinegar, and baking soda. Just mix ½ cup (118 ml) of vinegar and ¼ cup (68 g) of baking soda into a ½ gallon (2 l) jug of water. Pour it into the bowl, scrub the stains, then wait 1 hour before flushing. Then, follow it up with the Coke treatment.[6]
Vinegar is also a great disinfectant that cleans away bacteria.
Or, mix 2 parts borax, 1 part lemon juice, and 1 part Coke. Pour the mix inside the toilet bowl, let it sit for 1 hour, then scrub the stains.