brewer's dozen
After you finish your 12 pack, you find that extra beer in the back of the fridge.
Dude, I thought I just drank my last beer, but just found the final brewer's dozen.
Brewers Dozen
11 bottles/cans of beer. When you visit a brewery and are given a box of beer with one short, because the brewer drank it.
I got a brewers dozen of beer from XYZ brewery today.