How do I clean and deodorize toilet tanks?

You don’t say how bad it is so here is a simple solution. Get out as much water as you can and then if there is a “ring”, sprinkle yellow koolaide on it. It will dissolve the ring. You can use just plain bleach to clean & deodorize your toilet bowl. Always check and clean the tank too. Of course there are many toilet bowl cleaners on the market. You can always use a pumice stone (in toilet cleaning aisle) to scrub off a stubborn ring!

Once I clean the tank itself (using store-bought toilet cleaners), I always drop a bleach tablet in the back part of the toilet which keeps it cleaner longer.

Denture tablets dropped in tank over night "Denture tables do not contain toxic chemicals and are able to clean tough stains. Drop two to threedenture tablets in the reservoir before going to bed. Allow the tablets to dissolve and sit in the tank overnight. In the morning, flush the toilet and watch the solution clean your toilet bowl". or 2 cups vinegar in tank over night may need to scrub sides of tank with stiff toilet bowl brush just becareful not to move,or damage tank guts. Vinegar https://www.youtube.com/watch?v=kllNa2wtGWQ Not good to bleach inside toilet tank it can ruin rubber seals.

Vinegar can also eat away rubber if left to sit.