Can get a few things @ Castolon store, a bit under a mile east of campground. Very limited soda, bread, hotdogs, can of beans, etc. and ICE.

Big Bend National Park is very remote and it is preferable to bring in all the food that you will require. There are a few stores in the park, which mostly offer products similar to a small gas station convenience store. They are certainly not equivalent to even a small-town grocery store. The closest of these convenience stores is very close by in Castolon. It also happens to be one of the smallest in the park, but the others do not offer much more. If you need groceries while at Cottonwood, your best bet would be to drive the 45 - 50 minutes (one way) to the town of Terlingua, TX. Even there you will only find small-town grocery stores with limited selection. The closest big town with large grocery and big-box stores is in Fort Stockton, TX, 3 hours to the north.