Nowadays, a dealer who sells heroin almost always sells crack cocaine too, and vice versa. And because dealers are so paranoid all the time about getting caught by the police, they don't appreciate users blatantly asking them for drugs by their names heroin and crack. This is especially true when talking on the phone as they always believe the line to be tapped by the police.
So from the colours/slang terms associated with the two drugs, i.e. brown for heroin and white for crack...
Brown has become Brandy and...
White has become Whisky.
USER: Two whisky and one brandy! And hurry up, I'm clucking like mad!
Guy2:Yah, you wish MY Brandy Was Your girlfriend..Guy1: Your girlfriend?? Guy2: Yeah, She's da bes Girlfriend you'll neva have! Guy2: Don't count on it~
Also, brandy can be used as a verb, which is to mix or add brandy to something else.
Head in the hotel sippin brandy smokin reefa
And I'm so high ya boy don't lie
Hey Phil, how much did you brandy this sangria?