The fantasy world of Westeros has dragons, wargs, and neon green weapon of mass destruction. The universe of the show continues to surprise us as it nears its conclusion, but one thing we know: there's no way in the Seven Hells that Winterfell has a Starbucks.
Tormund Giantsbane gets his giant's milk macchiatos somewhere, but there's no way that there are coffee chains in the Seven Kingdoms.
If you're wondering if this is a joke: it isn't. The cup in question can be seen at the 17:40 while the Wildlings praise Jon and Dany may or may not begin to plot his murder.