Snortables refer to any and all drugs that can be snorted.
If you can't be bothered to name every powder you are carrying you just refer to it as snortables.
Tom: What snortables have you got lad?
Dealer: Got a few nice bags of M-cat and some beak that power!
Dave (Drunk, shouting at moving police van): PIGS! DIRTY FUCKIN' BASTARDS!
Ryan: Are you mad? Swerve that lad I have about 10 snortables on me you west head