Remove all trash, ash, and cigarette butts
Take out floor mats and wash them
Vacuum seats, carpets, crevices, and trunk thoroughly
Wipe down hard surfaces with an interior cleaner
Clean windows and glass inside and out
Shampoo fabric seats and carpets
Use an upholstery cleaner on headliner and cloth panels
Replace the cabin air filter
Run the HVAC system on fresh air, not recirculate
Clean air vents with a vent brush or compressed air
Place baking soda on carpets and seats, then vacuum it up
Use activated charcoal or odor-absorbing bags
Leave bowls of white vinegar in the car overnight
Use an ozone treatment if needed
Air out the car with doors and windows open
Repeat cleaning as needed for stubborn odors
Have the car professionally detailed if the smell remains