Clever one, that Black. Fabian suppressed any urge to shiver or otherwise react to Sirius' breath so close. His body instinctively tensed from it, but he managed not to do anything beyond that.
Once Sirius pulled away, Fabian exhaled, relieved and pulled his fags from his shirt pocket again, a little surprised they hadn't fallen from the flight. As he lit it between his lips with the tip of his wand, he moved to the edge, far enough away from Sirius so he didn't have to actually breathe him in. The view was, admittedly, spectacular.
"Think if you dropped a coin from here, it'd make a crater in the street?" he asked around a cloud of cigarette smoke.