How about “free”?
We just pull out the faucet in the sink, point it at the bowl (set to spray), turn it on and, on our system, push the two buttons that make for “flush only” (meaning no fill of the bowl). Ends the need for a toilet bowl brush too. Works like a charm and sizes the amount of fresh water used to the functional demand of stuff in the bowl. Always finish with a little extra to cover the joker valve.
The reason we adopted this was so we could effortlessly go back to raw water use when trying to conserve freshwater on longer cruises.
As I say, “free” and works better.
Jeff