I have always used bleach to sanitize my fresh water tank. One year I was a little heavy on the bleach and it took a couple extra fill and drains on my FW tank. I think part of my issue was that I did not drain my water heater and it took forever to cycle/flush the water through it.
As a side note, last week, I almost bought a bottle of Camco water "freshener" at Walmart. Says to add to stale smelling water (or something like that) to restore fresh clean tasting water. I looked at the ingredients (msds label) and says its Sodium Hypochlorite. AKA bleach. So for a pop can size of "freshener" they wanted something like 7$-8$. Just happen to have a gallon of bleach in my hand that was like $3.
Also note that you can buy different "strengths" of bleach. Ive seen anywhere from a 3% to 8% bleach concentrations. Check fine print on the bottle.
Ive also read that you can add vinegar to freshen up water.
My CPAP machine says to use 1-2 tbsp of vinegar to sanitize the water reservoir.
Another side note. When you see "Oxygenated" cleaners or sanitizers. Bleach Free, Sodium Hypochlorite Free, Chlorine Free etc - Think Peroxide - Hydrogen Peroxides etc. (I remember as a kid using Hydrogen Peroxide to clean small cuts and abrasions.)