|1.||I'll be back in a flask|
It originated from the term "I'll be back in a flash", but with the word "flash" replaced with "flask". It gives a double meaning now, where you can say "I'll be back soon" and also "I'll be back inside an alcohol containing vessel".
"Hey, dude, I'm gonna go pick up some more ammunition at K-mart. I'll be back in a flask."