AIBU to ask advice on eco toilet cleaning?

[Mustardfan]

I live in a hard water area and my toilet bowl gets very stained in the base (where the water is). How can I clean it/ keep it clean in an eco way? I have bicarbonate of soda, vinegar, borax substitute, as well as cleaners from the supermarket.

I know if you buy a cheap Coca Cola and leave it in there overnight should make most of it go away. Not sure if it's eco friendly though.

Thanks, I’ll try it, must be more eco friendly than domestos.