Sonic’s have public restrooms. All you need to do is ask for the key.
And Keene is the typical small Texas town.
Much of the town was build as a refuge for Seventh Day Adventists in the late 1800s, and is strongly tilted that way for now.
Is not a prosperous town but the local SDA college pays decent wages.
They do have a speed trap reputation but that is not as big an issue any more.
Seriously, just ask for the key.