This in fact is not a spoken word so much as a sound. It is the same sound made when someone is sniffing their nose as they are crying or trying to stop crying. The recovery sniffs is the sound you are mocking.
It is a sarcastic way to show someone you feel no pity for their situation.
Just like playing the tiny violin for a person, this mocks the persons sadness by "crying" along with them. See example
Bjorn: Yesterday, my girlfriend told me that my clothing is out of style and it really hurt my feelings.
Bennett: (very sarcastic)"Sniff-Sniff".... "Sniff- Sniff" oooh "sniff-sniff"...that's just terrible
Bjorn: Oh shut up
refers to powder cocaine only, not crack
"Do you know where to get any sniff sniff?"
When you sniff your fingers ,but make it look like you're thinking in order to smell your own ass under your fingernails.
are you doing a "sniff sniff"? hows it smell? MY TURN ?!?!?!?!!?