Bum Juice - 1. A cheap alcoholic drink, Mostly off brand malt liquor. 2. Any form of "street" brewed or distilled alcohol, made by homeless for the homeless. *note stay far from the latter definition, should only be used in small portions.
A bottle one has urinated in (typically in a moving vehicle), put the cap back on, and thrown out the window to be picked up by a bum that will drink anything he finds on the side of the road.