How to stop odor from toilet tank water?

Take the lid off the tank and put white vinegar in..Flush then make a solution of white vinegar and baking soda into a paste and rub the tank with a cloth. again flush.

The odor may be from mold spores in the water. Use bleach or hydrogen peroxide to kill any mold and spores in the tank.

That is a big red flag. First have your water checked to see just what is in there. You may not want to be drinking what ever it is that is making the tank stink. You may need a filter system. For 60 years, I have had well water with no filter system, & I have never had any smell in either of the toilet tanks. When the power goes out (I live in the sticks of NH - no power no well pump) I use the toilet tank water to wash my hands, it is that clean. I have 5-gal buckets of stored water for flushing & some drinking stored). I still have never had any smell from the tank at all. I do get my water checked also, and I still don't need a filter, so far. Knock on wood.

put javel int the tank let sit 10 min then flus 2-3 times don't let it sit longer