I don't want to panic you, but this is an extremely urgent situation. Your ferret will quite likely die unless you get some fluids into him - RIGHT NOW.

If you have a syringe handy, or an eye dropper, take up some of the soup in the syringe/dropper, scruff your ferret (by the back of the neck, the skin is loose here). Very gently open his mouth with the syringe/dropper and ever so gently squirt the soup into his mouth. He may shake his head and cover you in the soup, be persistent, his condition sounds desperate. You need to get fluid into him!!