I use Dawn in my tanks with about 5 gallons of clean water. Go for a drive and dump immediately. Sensors working just fine on this camper after 4 years (all tanks), and they don't stink. Now ... sometimes they DO "begin" to stink! The Dawn and a 30 minute drive, or a cup of bleach and 5 gallons of water (in the grey tanks with a 30 minute drive, and dump immediately), and smells gone (couple times a years).
Yes, it works. But you have to be consistent.
Actually, I think the driving with clean water does more good than all the soap and chemicals! That sloshing and pounding of the water on the sides of the tanks and on the sensors keep them clean.