To 'sub' a can of beer is to:
- invert the can, so the tab is pointing downwards
- use a sharp object to punch a hole as close to the base of the can as possible. By 'base' I mean the end that is the base when it's right way up.
- hold the can to your mouth so that the hole you punched is hard up against your mouth.
- turn it back the right way up
- crack the tab open.
- Drink. Fast.
Once you've finished all the beer in the can (shouldn't be long, as gravity and a sudden pressure change should make the beer flow from the can very fast indeed) you should (in theory) crush the can against some convenient body part, headbutt someone, and continue on your merry way, feeling like a right bogan.
Others advise me that this is also known as ' to shotgun' a beer.
'Subs' are also foreign language films which have been subtitled, with the original soundtrack left intact. Most movie buffs prefer 'subs' to 'dubs' as they leave the original tones of the original voice actors intact, and feel more 'authentic'. This is also important because in the case of some 'dubs' not only are the voices overdubbed, but the entire soundtrack is, with dodgy radio drama style sound effects used in place of the original recordings.
Sub is also an abbreviation of 'submarine', and depending on context this could refer to the submersible boat type of submarine, or the sandwich kind, as served at places like Subway.
... and finally, sub is also a popular abbreviation of the word 'submissive'. When used in the abbreviated form it usually refers to the one who gets dominated in a BDSM type arrangement.