I dont think many would want to pay $25+ for waterless, and if I did shell out the cash for a "car wash" and saw you walk up with a bucket of solution, pull out a towel, and start wiping the car down with what looks like water, then towel drying - I would be pissed. Not if you were my detailer and I knew what you were doing, but to an average "can you wash my car real quick" as you are using machines to polish, that looks pretty bad... But keep in mind I live in an area of $5-15 car washes with "under carriage spray, wheel cleaner, pre-soak foam, wash, spotless rinse, wax, and air dry" and more steps, or $25 "full service" washes.
If you have the stuff to do it, give them the experience - get a cheap soap like Mr. Pink or something, do a high concentrate and foam the whole car (they can take instagram/FB photos and tag your page for free advertising too), and let it sit for 2 min, then do your wash bucket and rinse. Wheel scrub + dry with spray wax for $5 more. Could that be 10 - 15 minutes on a quickie for you, and worth the $20-30 to them (whatever makes sense in your area) because soap making their car disappear = worth it.