I checked a few of the DVC grocery order forms and they have 2L bottles of coke, diet coke, and sprite listed at $3.99. If it is listed in the order form then it means that the resort shop normally stocks the product, the ones I checked are BLT, BCV, POLY, and AKV (order form is associated with Jambo's shop so you may need to go there if staying at Kidani), but I would guess that all of the shops associated with DVC properties would have them, and likely most of the shops on property, although I have never personally looked.