A friend of mine--let's not use his real name, so we'll call him "Spark Mavins"--was visiting DC from Maine this past weekend and suffered some sort of stomach virus which required repeated trips to the many bathrooms that our nation's capital has to offer. Unfortunately, in his haste he had to use port-o-johns and public bathrooms featured at the monuments on the Mall, which are strictly last resort options as far as I'm concerned--it's about on a par with digging a hole in the grass on the side of the road, using it, then covering it up with leaves all while being questioned by passers-by. Needless to say, Spark was a desperate man!
One of my frequent gripes is in many cities and towns most places have a "customers only" policy, requiring you to get some kind of key to use their bathroom or otherwise hoping to shame you into not just walking in off the street and making a bee-line to the facilities. Fortunately, I was raised with no shame, and when this guy has to go, he goes! And if they say "customers only" when holding that key-attached-to-a-broom-handle like it was granted by Charlemagne himself, I have no problem saying "I'll buy a coffee just as soon as I'm done, but you probably don't want me to decorate your floor here now do you?"
I understand the idea--if you own a restaurant you don't want your patrons to have to wait in line behind guys coming off the street, and you certainly don't want your facilities overloaded by too much use, or heaven forbid some street derelict who might fall asleep in there. But in an absolute emergency situation, tort law does have the doctrine of necessity (yeah I'm reaching here but so what) and if the user is willing to fork over a couple dollars to use the facility then why require the fiction that they purchase something? Of course it'd also be nice if the city had a number of well maintained public restrooms, but who are we kidding.
In the meantime, I suggest hotel lobbies--they never ask if you're a guest there, and these bathrooms are usually well-maintained. And this city has plenty of hotels.