I got away from my conference with a dash to the Carousel Cafe. It's located, appropriately enough, next to the carousel that is perched on the roof of the Moscone Center. As you come up the stairs it may not be obvious---if you face the carousel the cafe will be directly behind you.
They have a good selection of sandwiches but I ordered iced coffee and a shortbread. The proprietress mixed it with milk for me on the spot---shaken, not stirred. It was a great pick-me-up.