By Daniel Kline Fast-food chain Burger King has done something you’d be more likely to expect from Chipotle or Starbucks. Fast-food chains face a lot of negative optics. The biggest one, of course, is that hamburgers and fries or even burritos filled with sustainable ingredients (which include cheese, sour cream, and guacamole) aren’t very good for you. You can make better choices at some fast-food chains than others, but in this restaurant genre, your salad likely includes bacon, ranch dressing and, perhaps, fried chicken. On top of that, fast-food giants like Restaurant Brands International’…