Since this is a very related question, it prompts me to ask something I was wondering.
On subsequent days at a water park, you can purchase just the barcode to get another day of sodas with your mug. This is cheaper, because you aren't buying the souvineir mug itself a second time.
I frankly have enough mugs, and don't need another one as a souvineir. In fact, I only continue to buy the resort mugs each trip because it's required by Disney rules. At the waterparks, can you buy the barcode and use it on your resort mug? Or does the barcode have to go on a waterpark mug?