I use Chemical Guys Inner Clean Interior Cleaner. It cleans up most stains and smudges, leaves behind a bit of UV protection, and, best of all, smells like pina colada. I also use it to clean fingerprints off of the center screen. I keep a small spray bottle of the stuff in my driver side door along with a MF towel.
Once in a while there is a stubborn stain that requires something a bit more powerful. In that case I use Chemical Guys Leather Cleaner. Even though the seats are a vegan leather, this cleaner still works great.