The water-soluble material in coffee beans (1-2.5% caffeine) and water-extractable oils (10-15%) represent a small percentage of the total bean. There is a lot of carbohydrate (~50%), not all of which is soluble, and some volatile oils (not so tasty).
The bean is not totally soluble in anything, but when ground very fine, it could be dispersed in a thick suspension (or a thin suspension, if you keep shaking it up). I wonder what coffee material is used in coffee-flavored ice cream: ground beans, powdered instant? The ground-up bean would probably be a good source of dietary fiber.