For a moment, Renji stared, trying to figure out what the guy's point was. If Brook was used to not breathing, oh, okay, that made sense.

"Oh, I got it. You're in the dead guy club too." Renji nodded, proffering his fist to be bumped while he continued eating with the other hand.

Obviously Brook was no Shinigami, but considering Renji was the only one these days... well, he wasn't going to get too picky about it. Take your buddies where you can and all that.