For curious monolingual folks like myself, the labels on those bags (haricots de Soissons) indicate that they’re full of beans. You can see a similarly NSFW example of a postcard referencing General Oku Yasukata here along with the following explanation:

…In French, “au cul” means “at/on the ass.” Thus, as Linhart explains, “Oku” and “ass” are homophones in French, restricting the pun to a play on the French figure of “General Ass.”