@ossobuco,
Wine is not just made from grapes. Dessert wine is made from many different fruits. I don't like the taste (too sweet generally), but its holds it's place on shelves of many liquor stores. FWIW, there's pineapple wine, and of course, Italian families have been making dandelion wine for centuries.
Sake is a ferment made from fermented rice. Generally, it's 15-18% alcohol, which I understand they dillute it down to around 15% when they ship it.
Plum wine is another fruit wine (popular in Korea, japan and china), but not connected to sake in any way that I know of.