Any of the DVC resorts sell basic groceries in the resort gift shop, like milk, juice, cereal, bread, peanut butter, lunch meat and cheese, crackers, fruit, doughnuts, chips, etc. Even the regular resort gift shops usually carry an assortments of drinks and basic snacks. For example, when I was at CR last week, I could have bought individual milk, soda, chips, candy and other snacks in the sundries store. At their quick service location, I could get sandwiches, chips, juice, fruit, milk, soda, and bottled water.
DVC gift shops would be located at Beach Club Villas, Boardwalk Villas, Villas at Wilderness Lodge, Saratoga Springs, and Old Key West. I haven't been to AKL since they started the conversion to villas, but they should be carrying food items as well. There are also three Hess convenience stores on property where you can get basic foods.