User blog comment:Charmeleoness/Drinks/@comment-3146930-20140729221950

Ruby likes milk because she feels drinking milk will help her grow up big and strong. The coffee thing always reminds me of Justice League; in one episode the Flash is asked how he takes his coffee responding "cream and 37 sugars."

Weiss may drink coffee from a tea glass because it looks more dignified and doesn't want others to know she is just like them instead feeling above them.

Blake likes tea and it is supposed to be calming, possibly to calm her down because she lives in constant fear of being arrested.