The real point of the demonstration was to emphasize that cover is determined by the weapon/cartridge being shot, not by the object. It was also to encourage the viewer to do empirical testing of his personal defense weapon/loads whenever possible to determine how they penetrate and what constitutes cover so you can also use that knowledge AGAINST the bad guy.
For the record, future episodes (probably next week's rerun) will include one-gallon jugs of water in the fridge.
Even if we did pack the fridge with different stuff, there's no guarantee that we'd ever hit the same chunk of food the same way twice. At least with the empty fridge, we achieved consistent resistance for all impacting rounds. We also quantified keyholing and pentration on the exiting side. To me, that IS more relevant than a TV dinner that happened to stop a 9mm while a .40 penetrated a head of lettuce...
And, yes, shooting beer is just plain wrong...
Stay safe,
Mike