Peter stepped back, still sleepy enough not to notice anything untoward in Sirius' behavior. Of course, Sirius could have started humping Peter's leg and it wouldn't have seemed too untoward. It was, after all, Sirius. "It's one in the morning. You might have called. Sent an owl. Lit a firework with a message in."
He was awake enough, however, to notice the smell of alcohol. "Should you be drinking?" he asked through a yawn. It at least answered the question of why he hadn't lit a firework. The open flame would likely have had a bad effect on him.