Odor: mylar and other metalized based wrappers (chips, energy bars, oatmeal, Mountain House etc), cans (soda, canned coffee, beer) and glass bottles (again beer) are designed for long term storage without oxygen getting in. This also means that they let very little odor out. Thus, it is reasonable to expect that these food coverings would not be sources of appreciable odors for bears. You could even put a high odor food (jerky) in a canning jar or mylar bag to provide a good odor barrier. This said, any traces of food that you put on the objects might be smellable. So, don’t store these items with your jerky prior to the journey!
More importantly, any other food residue in the car is odoriferous. My car is well used, so those cheddar rockets stuck between the seats, that peach pit and samosa wrapper from Fresno, or Schatt’s bakery bags, and the Purell would all be odor sources that may attract a bear regardless of how odor proof your energy bar/beer is.
Visibility: A covered trunk would work to screen food in a sedan, but it is difficult for those of us with other cars (I’m sure none of us own a Subaru
). You could put a few energy bars and a bottle of water in the spare tire well. I place my post-trip change of clothes on the driver’s seat, not in a bag that might attract a bear. Also I don’t bring deodorant. I’ve heard stories of river rafters being harassed by bears that knew how to open, and liked to drink beers. This illustrates that bears are clever, and quite able to recognize that a non-odoriferous object may still contain food.
This doesn't really answer your question about the cooler, but does address the general problem of leaving post-trip food in your car: clear out your trash and put suitably wrapped foods in a place that a bear can’t see.
