i've had pretty good luck using dawn dish soap. Dilute it way down, start with a 1/2 teaspoon to a bucket of water, spray on let it sit for a minute or so then vacuum off with a wet dry vac.
There are cleaners you can get specifically made for auto fabric, you'll be able to see reviews of them on different websites such as amazon.
Whatever you try, try first in an area that no one sees.
That's a LOT of Dawn and that stuff is seriously soapy... exactly what you don't want. That's the amount that you use to wash a sink full of dishes. I should know because I have never owned a dishwasher.
If the seats aren't leather and you are 100% about that, get some over the counter leather cleaner from your local auto store. The cheap stuff, not anything expensive. Keep this in mind. The stuff you are cleaning is DYED. If you rub on it too hard, you will rub the pigment right off the seat. If it doesn't come off easily, rubbing harder may yield you undesirable results. If you have allowed the stain to remain on the seats for any significant amount of time, it probably ain't gonna come out unless you have some really crappy hard vinyl seats.
Interior stains have to be addressed IMMEDIATELY. If you don't, they become permanent rather quickly.