Why don't coffee cups work on Fridays? Because they've been mugging all week and need a break!
In this dad joke, we learn that coffee cups don't function on Fridays because they've been "mugging" all week - not stealing, but simply holding our coffee! They've earned a well-deserved break from their caffeine-carrying duties, delivering a humorous take on why your cup might feel a bit sluggish at the end of the workweek.