Couple of options, one will work with 100% certainty.
1. Find somewhere to rent on Ozone Machine. These are machines used by hotels to get the smoke smell or any smell out of a room. Cleaners also use these machines to get the smoke smell out of clothes and curtains that have been in a house fire. CAUTION-you cannot be in an enclosed area where an Ozone Machine is running. Also, do not have anything wet or any moisture in the carpets or seats. An Ozone machine will turn a water molecule into hydrogen peroxide (bleach) and ruin your fabrics if they are wet. If you cannot rent one you may want to talk with a local hotel owner or dry cleaner and see if you can work out a deal. Run it for 24 to 48 hours and the smoke smell will be completely gone
2. Buy a big bag of real lump charcoal. Lay the bag flat in the back seat and filet the bag open. Don't let it spill but make sure the charcoal is exposed to the air in the car. Get a box fan and put it in the front seat. Don't point it toward the backseat because you don't want to shoot charcoal dust all over your car. Just make sure it is running and moving air around the car. Make sure all of the windows are rolled up and let the fan blow for a day or two. The charcoal will pull the smell out of the car. This trick is used by people that work on RV's to fix food that has rotted in the fridge. Many people will drop off RV's and forget that they have food in the fridge. It will sit out in the sun and smell worse than anything you can imagine. Maggots, bacteria growing. Even pulling the fridge out and bleaching it will not remove the smell. Stick a bag of charcoal in there and and run a fan and 24 hours later the fridge smell brand new.
That is all I got. Try the charcoal trick first but don't go buy those cheap *** brickets, get you a bag of lump charcoal. When you are done with the charcoal and the car is smoke free, crack a beer and grill you a steak with it.