If WDW has bottled water, it is Dasani.
If you have a car, a few suggestions we like: The Hess near the
AAA Car Care center is larger than the one near the Bwk.
There's also a convenient Whole Foods just off I-4 at Sand Lake Rd. (take north exit from airport) No hard alcohol, but they have all kinds of craft beers and wine. Whole Foods also has fresh squeezed juices. We like getting arrival day lunch there, because they have tons of options. They have all kinds of soups, hot bars, cold bars, seafood, bbq, brick oven pizza. The seating area is quick serve, but very nice.
There's also multiple Publix stores just off WDW property. We don't buy alcohol, but they also seem to have a pretty big selection of beer/wine. A fair number of prepared foods, and all the ordinary stuff.
We've gone both ways regarding grocery stops or not. Water is always a must, and we're pretty big on having a car. One hidden advantage of a stop, is lighter packing. We buy sunscreen, etc.