The STDs you get from having sex or doing sexual favors in a McDonald's bathroom, McDonald's table, McDonald's counter, ect.
Mike: -awkwardly- Dude, I found a bump on my penis...I think its herpes.
Caleb: Woah, dude are you serious? How did you get that?
Mike: Uhm...I did this chick in McDonald's bathroom.
Caleb: Damn, dude you must've ordered the McSTD.