Starbucks Coffee
441 Stuart St #L9, Boston, MA
0% positive
Directions: Starbucks is on the corner of Stuart and Dartmouth. Bathroom is in the back, next to the door into the shared hallway of the building.
Comments: You should probably buy a coffee or something, but I've used it when I really need to pee before catching a train (the bathrooms at Back Bay are disgusting, and also gendered) without buying anything and not had a problem.