How do you clean a stained toilet bowl without chemicals?

chemicals in a toilet are generally safe for septic tank use, close the lid for a few moments if you are concerned about your pets.

Coca Cola, Vinegar, Baking soda, etc., will not do an adequate job of sanitizing .... and all these are 'Chemicals' to some degree ....

Thank you for your help. I have used vinegar and baking soda, with no luck, brown stain is still in bottom of bowl since we move here. Also have used toilet cleaners just want safe products as moving to organic certified property soon and the toilet in that house has not been used for long time and bottom bowl is completly stained too.

Have you tried using Thieves cleaner from Young Living?

you may have to resort to using a pumice stone - just be sure to keep it wet to minimize damage to the surface;

https://www.hunker.com/13420891/how-to-clean-a-toilet-with-pumice-stone

which of could result in scaring ( damaging the porcelain surface by fine scratches which will continue to collect sediment) but once you get it clean, it may be easier to KEEP it clean. Thank you for having respect for your land.

https://www.hunker.com/13420891/how-to-clean-a-toilet-with-pumice-stone

We had to go with the pumice stone on our older porcelain toilet. Worked very well with no problems with scratching. Cleaning weekly with baking soda now keeps it fresh and clean!