The GEO method may work, in this you add half a cup each of DAWN (originalm not anti-bacterial) and Calgon Water Softener (Liquid or powder matters not) and about 1/3 tank water,, Drive, like 50 miles, turning corners and otherwise sloshing it around normal driving, no special course needed.
Then dump and flush
After this procedure the sensors will still show full for a few hours (Full of soap bubbles) but they may go to empty.. Till you use the tanks again. That's all the longer they are good for
The "Sensor Cleaner" stuff at Camping world and other places..........
I have compared the labels on assorted chemical additives both with and without sensor cleaner. The differnce.. The cleaner products contained salt, Good old table salt, that was the only difference. . Thus the "Cleaner" is salt.
Which basically is useless as far as cleaning the sensors is concerned.
I might add my opinion of most of those chemicals is also "They are useless" save for transferring your hard earned money into CW's corporate pockets.
If you want working sensors.. Google SEE LEVEL SENSORS
Oh,,,, Some of the tank additives are not chemicals, they are biologicals.. IF you can go 2 or more weeks without dumping.. They MIGHT help.