The dealer I bought my RV from recommended Tanktechs rx. The bacteria in it kills bad smells, doesnt just mask them like others. I’ve gone a week in high heat without emptying my tanks and no foul odors whatsoever.
The one downside guess is you have to remember to NOT empty your tanks completely. The directions say to leave an inch of liquid to maintain the bacteria that has built up in the tank. It might be difficult for some to know how much is left in your tank.