Green’s Dictionary of Slang

(Irish) a can or bottle or draft of Heineken beer.

2000		P. Howard Miseducation of Ross O’Carroll-Kelly (2004) 129: I’ll get the borman to stick a pint of Ken on for you.
2005		P. Howard Curious Incident of the Dog in the Nightdress 17: He [...] puts another pint of Ken in front of me.