Hi Laura! I applaud your efforts to reduce your plastic footprint. Unlike Kermit, it's easy being green these days.
Yes, when asking for water at most Walt Disney World Resort Dining locations, you will be given a disposable cup even when refilling a water bottle due to the local food handing laws. Disney does do its part when it comes to
recycling, though. And there are several options to avoid disposable cups if you plan your day just right.
There are of course water fountains all over Walt Disney World Resort, usually near restrooms. Some people don't like the taste of Florida tap water, but there are easy solutions, like bringing a bottle with a filter or those water flavor-enhancing beverage stick packs. Some table service restaurants will sometimes have big drink dispensers of water (sometimes flavored!) sitting just outside their entrance that is free for all. And don't forget to fill up before leaving a table-service reservation.
Another option would be to specifically seek out the
quick service dining locations that have self-service beverage stations, as they also have filtered water spigots. Your options would be both Satu'li Canteen and Restaurantosaurus at Disney's Animal Kingdom, The Electric Umbrella in Epcot, and both Earl of Sandwich and Wolfgang Puck Express at Disney Springs. Be Our Guest in Magic Kingdom Park does have a self-refill machine, however you'll need a reservation to get in. And there are of course the quick-service locations at all Disney Resort Hotels. You'd be under no obligation to purchase anything to get water at these restaurants, so just walk on over and help yourself. But pro tip, bring a wide-mouth bottle to make it easier to fill.
I hope this helped, Laura, and we'll see you real soon!
~Kristen