Sirius felt a little bit guilty about smoking when Harry didn't rise to the bait -- and that, he knew, meant he was being immature about the whole thing -- but it was pleasant, especially with the beer.
Surreptitiously, he cast a charm to move the smoke up, so at least it wouldn't physically bother Harry, and frowned slightly as it took two attempts. He was jolted out of his worry by Harry's laughter. Looking, he realized that Lily must have set it off, somehow.