I believe you will find everything and more in any big(Mamouth, Leclerc,) shopping
center as in the states. But there are outstanding products available, like cheeses of all sorts, patés de foie de canard(duck liver pate .. delicious), and in general very good food
, wines and vegetable. But everything will be more expensive compared to the US, mainly due to the poor shape of th US dollar, compared to the Euro. Brest being a port of entry, you may have all the liquors, wine and some other products duty free if you apply for that. Might be worthwhile. Bon apetit!