Bottled drinks (sodas, Powerade, iced tea, etc.), milk, Nesquik, juices, etc. are all allowed under the DDP.
If you are on the DDP, have a refillable mug, and plan to eat at the hotels, it's always best to get a bottled drink with the meal, but then drink from the refillable mug. If you do it that way, you can either bring the bottled drinks to the parks with you or save them to take home.
Normally, the mugs are only good at your specific resort, but this year, all the mugs are themed the same with YOMD, so they can be used at any resort.