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I would use a clean white cotton towel (white so you can see the dirt) that is lightly damp and wipe the seats down. Use any spot remover as needed. Same applies to the steering wheel. I'd avoid any chemicals as much as possible.
I had alcantara seats in my last car, which had a couple arrow head hunting trips on the side of the racetrack. I never used anything other than water and a cloth as 5DOT0 says and they looked brand new when I sold it. Same can't be said for the headliner, never could get all the little plant pins out of it.