The term originated in the Down-Low scene amongst African Americans in Atlanta and is played as a party game. In gay orgies, a bro would approach another bro with a Smirnoff Ice and hold it on his scrotum. After the bro's scrotum is chilled, he drinks the Smirnoff while the other man gets down on one knee and performs oral sex on him. The goal of the game is to finish the drink before ejaculating (icing) in the other man's mouth.
Michael: "No, how?"
Andy: "Gave him a box of cereal which contained a tall boy of Ice. What a breakfast."
Michael: "Damn gotta love Bros Icing Bros."
Bro: "Bro, I just totally iced you bro! Take a knee and chug!"
Non-Bro: "Um. No. I'd much rather enjoy this beer instead of drinking your piss-water bitch drink. I can't believe you spent money on that fruity flavored garbage you worthless piece of shit."