Yes. There is a gift shop in the Yacht Club has does have some basic supplies. However, the gift shop at the Beach Club (which is attached to the Yacht Club) is better stocked. The Beach Club shop includes a mini convenience store.
The selection is not large, but you will find some basics like milk,
juice, eggs, bananas, butter, yogurt, cereal, dry pasta, a
loaf of bread, sliced
cheese, soda, etc. There are also snack items for sale as well as beer
and a small selection of wines. For my family's tastes, I'd be able to
find
the makings of a basic breakfast or lunch there, but for dinner I'd
need another source of supplies.
If you're looking for personal care items, these can be found in the shops at all the Disney Resorts. If you look at the post
HERE, you'll find a list of what is typically available for sale.
Good luck with your planning!