Apres event ride is pretty common on some group rides I have done - but that's when no more riding is planned until the next day. I've never ridden while drinking or ever seen it done, to my knowledge.
I did ride (once) with a guy who admitted to being stoned at the time. Funny...we had to stop at a convenience mart for Reeses' peanut butter cups. Go figure.
Apres ski beers are pretty common, too. I once told a friend that I didn't like to drink after skiing, "because it goes right to my head." He looked at me kind of funny and said "Duh. That's the whole point!"
Ah, well. Different strokes.....
2007 Seven ID8 - Bontrager InForm
2003 Klein Palomino - Terry Firefly (?)
2010 Seven Cafe Racer - Bontrager InForm
2008 Cervelo P2C - Adamo Prologue Saddle