I hadn’t come across this phrase until I heard a senior policeman complain about the relaxation of the licensing laws by the Labour government. Instead of a continental European-style civilised cafe society, the laws brought a veritable Pandora’s box of social ills in the UK: binge drinking and violence. Much of this is reputed to be down to bars which are optimised for consumption and profitability. In the same way that business meetings held standing up are more efficient, the same is also true for drink consumption. According to a New Stateman article I found:
Drinkers who stand consume more than those who sit down, so take out the chairs and tables and encourage “vertical drinking”; remove all flat surfaces and ledges so that drinkers have to hold on to their drinks; those who talk drink less, so turn up the music.
The nature of standing up is the vertical and vertical drinking. The Standard (Hong Kong) has a great article on the impact of vertical drinking.