The residual garbage you are left with after a failed sexual experience; an unfilled condom.
#1
Evan: "Sammmmmmaaaaaayyyy did you lay a fat nut on that chick's face last night?"
Sammy: "nah man... she made me use a condom, so you know I was left with an empty sack."
#2
Eric: "Hey Gabe, why are you in such a bad mood, bro?"
Gabe: "Listen Brother, you'd be in a bad mood too if an empty sack was sitting YOUR trash bin."