Green’s Dictionary of Slang

jerker n.1

[jerk v.2 (6)]
(US)

1. [late 19C+] (also soda-juggler) a soda-fountain clerk; usu. as soda-jerker.

2. [1950s] a bartender; in combs. such as whiskey-jerker or beer-jerker under beer n.

3. [1930s] a drinker; often as beer-jerker under beer n.