We always call the dog! He's a black Marley, eats most anything.
I have taken seats out of the vehicle and used a scrub brush and laundry detergent, then rinsed with a hose. You can use a detergent and warm water scrub and then use towels to pat it dry. If a stain persists, after all has dried, get some interior cleaner at the parts store, or WalMart. Prestone makes one that is in a red can and has a brush attached to it that works great. Spray on, rub in and vacuum when dry.
Theeasiestt way yet is to find a detail shop. These are the car wash places that pop up in old service stations and such.Usuallyy just a couple of hard working guys trying to make a buck, but man can they make a car look new! You can probably get that seat cleaned for twenty five bucks or so and not have to fool with it yourself!