A gentleman who considers it absolutely no bother to consume 6 litres of vodka over a music festival weekend. Whilst it is unlikely that a "6 Litre Joe" would consume the vodka straight from the bottle, it is perfectly feasible that he would fill up a pint glass with equal measures of vodka and mixer.
Bish: "Ooooftt whit! That boy in on his sixth litre of vodka in two days"
Marco: "Aye san, i've been watching his progress- he is a 6 Litre Joe if ever I saw one"
Somebody who takes great delight in consuming ecstasy - which is sometimes shortened to "Eccy". Eccy Crunchers can usually be seen wandering around nightclubs with dilated pupils and eyes wide open. It is unlikely that an Eccy Cruncher would make in intellectual conversation
"See those boys over there? They're all eccy crunchers"