Well, the moment he reaches for a tall glass of mead the fridge suddenly jumps at him! It knew that Marty would always be sure to wash it's windows before opening. The magical fridge senses that whoever is grabbing the mead would not be an employee, seeing as an employee would not find the keys without Marty in the first place. It knew that Marty had left the premises temporarily. So it considered whoever was here to be a thief! It's sides grew terrible teeth and the fridge door tries to slam him inside the fridges maw. The drinks have been teleported to a pocket dimension as the inside of the fridge becomes a mouth, leading to places unknown.