Remove all trash, ash, and cigarette butts
Vacuum seats, carpets, floor mats, and trunk
Wash or replace cabin air filter
Clean hard surfaces with an interior cleaner
Shampoo upholstery and carpets
Steam clean fabric seats and carpets
Wipe down windows, headliner, dashboard, and door panels
Sprinkle baking soda on carpets and seats, then vacuum it up
Place activated charcoal or odor absorbers in the car
Leave windows open to air out the vehicle
Run the fan and air conditioning on fresh air mode
Replace or clean floor mats
Use an ozone treatment if the smell remains
Have the car professionally detailed if needed