I'm finally able to read this thread!
I'm getting ready to head to Winona in two weeks. By what I have been told, you need to bring in 6.5 oz. and 10 oz. empties in order to get filled bottles. They only accept paying a deposit at the bottler by some local people/businesses. You can get 16 oz. Coke and Diet Coke in 8 packs at the local grocery store (IGA?) and pay 20 cents a bottle for deposit. They used to also carry 16 oz. Sprite, but I have not seen them there the past few years.
6.5 oz. is only Coke
10 oz. is Coke, Diet Coke, Mellow Yellow, and Sprite (you can use any of these as empties - you don't have to have the exact type you are refilling, so you could bring in Coke empties to get some Sprite).
They also do some 10 oz. (Sun Rise?) flavors and 10 oz. Barq's. Markito told me that you have to have Barq's empties to get filled Barq's.