Don't smoke. Smoked once though when i was a child. All i remember is nicking a fag and hiding in the toilet late at night. Dont blame me, there were a lot of people around me at the time who smoked so i thought i'd give it a try haha.
I imagine Sherlock doing this when there is a lull in cases and John has confiscated his cigarettes and his gun. This is him trying to get John to buy him some more nicotine patches, but John is having none of it. "Stop ignoring me Jawn. I need them!" "You said that last time Sherlock. The answer is no." "Please." "Still no."