Go out to your car with the following supplies:
Open the passenger side door. Clear everything off of the seat. If it’s trash, it goes in the trash. If it’s something necessary with no other home, put it in a box. If it’s something that can find a home in your house, put it in a separate “for the house” box. Repeat for the passenger side floor, and the inside of the door, if there’s storage there. Take the floor mat out and shake it out. Vacuum (if you can) the seat and the floor. Put the floor mat back. Wipe the plastic parts of the inside of the door with a wipe or three. Take a break.
Open your driver’s side door. Sit in the driver’s seat. Go through the center console the same way you did the passenger seat: toss, box, vacuum, wipe. Vacuum the driver’s seat and floor and shake out the floor mat. Wipe down the plastic parts of the driver’s side door with wipes. Take a break.
Open the rear driver’s door. Repeat the process for each seat, taking a break in between.
Pop the trunk. Take everything out. Vacuum it. As you handle each item you took out, either toss it, box it, or find it a home in your house. Bring the “to the house” boxes to the house. Put the “no other home” boxes in the trunk. Windex your windows if you have time.
Keep in mind, car washes always have vacuums and garbage cans available. Just remember to bring quarters. Lots of them.