Isastegi Sagardo Naturala Basque Cider 750ml

When Sand says "sour wine," she is referring to cider.
So, I asked Andy to suggest a cider that might have been in the style Sand would have had in the house. And Andy said:

"Isastegi Sagardo Natuala Basque Cider! I love this funky Basque Cider, but it's not for everyone. Made in the traditional Basque style, Isastegi is organically farmed and produced without added sulfites and left unfiltered and fermented completely dry. Expect flavors of orchard floor, yellow apple skin, pear and a pleasantly yeasty funk. Isastegi pairs beautifully with seafood and cheeses." And George Sand.