Possessives and Attributives
Q. How do I refer to the burgers at McDonald’s, given that the name already has a possessive apostrophe ess in it? If I say “McDonald’s burgers” then that is just burgers belonging to McDonald, but “McDonald’s’s burgers” feels wrong to me.
A. A possessive name like McDonald’s applies not only to the business itself but to anything it produces and anyone it serves. So McDonald’s restaurants sell McDonald’s hamburgers to McDonald’s customers. And though double cheeseburgers are a thing, double possessives are not (except, technically, in a phrase like “a friend of mine”; see CMOS 7.26).