Whenever I have been there, they would NOT accept QS credits and would accept snack credits only for certain items, waffle sandwiches not included. It was somewhat entertaining watching people wait in the line, walk up to order and only then be told that they couldn't pay for the sandwiches with the dining plan.
However there has been a recent post from someone who says that now you CAN use QS credits for waffle sandwiches (although not for the Nutella waffle which also doesn't count as a snack). Unfortunately they did not go into what would count as a dessert or beverage. And that one post is the only place I have seen that information.
If you are asking if a side dish comes with the waffle sandwich, no it doesn't. You get only the sandwich. If they are taking QS credits for it, you should be entitled to a drink and dessert (although as noted I've never seen anybody say exactly what would count as a drink or dessert.)
