If you just use bleach and have a odor, or maybe there's a plastic odor from it not being used much, you can dump a box of baking soda in the tank and let it sit for a while. If you've already sanitized and flushed it, you don't even have to drain and flush the baking soda out. I pour bleach, baking soda, antifreeze, etc., into a 2 liter soft drink bottle, then dump it into my fresh water tank. The bottle's neck is a perfect fit for the fresh eater tank fill.
2011 Sunseeker 3100
1997 Pathfinder Toad