Unless you're in the south you mostly don't have to specify unsweet for the tea (unless it's something that sometimes but not always comes with things mixed in like chai). Coffee should be that as well in theory but so many people drink it in different ways that if you just order a coffee or espresso or whatever you'll get asked if you want it black (and dont get me started on restaurants asking if i want my martini w vodka ir gin). Chains have (or had, it's been awhile for me) their own lingo as well, like at dunkin a "large regular" meant 2 creams and a sugar (or maybe 3 and 2, I can't remember)