What is Cadbury Drinker?
Someone who gets drunk off a small amount of alcohol.
Cadbury's chocolate blocks are advertised as having a "glass and a half of full cream dairy milk" in every block.
A "Cadbury drinker" gets pissed off about a glass and a half of beer.
Look mate, Matt's had half a shandy and he's rat-arsed already. He's such a Cadbury drinker.