The average person passes between 400-600ml urine in one secretion.
Flushing a toilet uses 9-12 litres of potable water.
I have a bidet in "my" bathroom (to wash my privates.)
Recently, I have taken to also using it as a urinal as well. At my age with my prostate, sitting down is far more comfortable and productive. When finished, I use the mixer tap to wash down any residue using only about a cup of water.
I dared to suggest to my wife that women should also have a urinal available to pee in, instead of wasting large amounts of potable water to flush.
Her response was that urinals are smelly and barbaric...!