Wiktionary
n. A trip made, often late at night, to obtain beer or other alcoholic beverages.
Usage examples of "beer run".
An attack on the Prez would have been bad enough, but under those circumstances -- a police-planned beer run -- it would have been evidence of the foulest treachery, a double cross, and the Angels would have done exactly what they all came to Bass Lake expecting to do.
I made a beer run before going back to give him his bath and his place a bit of cleanup.
Who'd have figured that leaving on a beer run would end up with me freezing to death in a range of mountains that never even existed?
On his second night there he made a beer run into town and Yankee Doodle Dandied himself right off the highway and into Hickory Nut Gorge.
If he reported that I went on a beer run, well, wouldn't nobody take it seriously.