Coke isn't great for removing oil, fat, or grease-based stains. For these, you're better off using dish soap, detergent, or a stronger acid like vinegar.
Coke won't remove stains caused by inks, dyes, or pigments (see also 'How To Get Ink Out Of Fabric'). Rubbing alcohol and other chemical solvents are better cleaning solutions.
1. First, flush out most of the water from the toilet. Either turn the knob on the side of the tank to turn off water flow and then flush the toilet or fill a large bucket with water and dump it quickly into the toilet. This will force the toilet to empty.
3. Then, wait for at least two hours for the Coke to work it's magic. 4. After the time is up flush the toilet and use a scrub brush on any remaining stains.