Sirius hated everything about Snape - the way he acted, the way he looked, his very attitude. Hated them all with a passion. And he really hated his voice, that slow lazy insolent drawl he affected, as if by drawing out his words, he raised his level of self-importance, announced listen to me. He couldn't help but think that he reminded him of certain of his professors, which was not a good thing.
He really hated the attitude he was taking toward Remus, as if Remus were nothing. No less than nothing. An irritant, an interruption to his otherwise perfect day. Except that Sirius knew better - knew that everything annoyed Snape because he was a very unhappy boy. And a stupid git.
Nonetheless, he swallowed his pride, and spoke up before Remus could reply. He was the reason they were there after all, it was up to him to say something first.
"Not him, me," he attempted to direct the Slytherin's attention to himself. He knew the hatred he felt was quite mutual between them. He knew Snape knew he was there, whether he wished to acknowledge the fact or not. "I've come to apologize for... the other night. It was a prank that got out of hand. I never meant for anyone to get hurt. I'm sorry."
Perhaps his tone was as stiff as his back, but at least he hadn't said the words through clenched teeth or with a threatening demeanor or anything of the sort. He wondered how long Remus would insist on standing here before they could leave this place and do something more fun.