I parked at SMF once. I think it was 2012 during a 3-day holiday weekend. Wasn't sure what I needed to do and got there really early. But I figured I didn't need to mess with anything else and just went to the onsite daily lot where it might have been something like $9 a day. Looked it up and it's still pretty cheap at $13 a day.
Barely had any baggage though, so that helped. My big worry was that their shuttle service would be low frequency at 5 AM, but the bus was just about to leave when I got there so I didn't need to wait long. I was worried that I might need to walk or at least wait a while in cold weather.
It's certainly a different kind of airport, where very little was developed around it. Maybe a few warehouses, but otherwise still surrounded by farmland. The closest thing I could find to off-site parking was a special rate at a hotel about 3 miles away. Apparently up to 8 nights of overnight parking with the room rate. I don't see an option just to pay for parking without a stay. Another nearby hotel has a free hourly shuttle to the airport, but I don't see any options to park longer than needed for a hotel stay.
https://www.marriott.com/offers/par...ento-international-airport?propertycode=sacfp