Why would anyone need to do that?
At the places I've been to where normally single-sex toilets were designated as gender-neutral, they were labelled according to the plumbing they contained, so anyone choosing that particular facility was aware what was in there. (And single-sex options were also available.)
I've only had one experience of this, and it wasn't good.
I briefly lived in a hotel that was originally created as male-only worker accommodation in a 'company town'.
(AKA single quarters.)
The facilities on my floor were designated as shared male/female, as the 'hotel' had expanded to provide accommodation for the general public.
(The internal layout was: shower and toilet cubicals opposite each other in one area, separated by a row of mirrors and sinks, and urinals screened off in another area at the opposite end of the floor.)
One morning, I was using the urinal, fully clothed, and a woman and her daughter walked past several partitions, in a cattle run structure, all of which said "MEN ONLY BEYOND THIS POINT" until they reached the urinals, and proceeded to do the 'invasion of the body snatchers, point and screech'.
The woman made formal complaints to the police, the hotel and my employer.
I was very fortunate that the complaint was not upheld, due to the many, many signs, in place, and I didn't end up with a permanent record as a 'sex offender'.
(NB. Many people, typically drunks, have ended up on a sex offenders' register for the twin charge of: indecent exposure/urination in public and it affects them for life.)
As I'm sure you can imagine, this experience makes me very uncomfortable with using urinals, and doubly so about shared facilities.