A great place to sneak kill an enemy after hitting them with a bottle is in Chapter Two, in the area after the zombie that is banging on the door. Go up the hill to find a zombie next to a campfire. Grab one of the bottles from the ground, and throw it at his head. It is important that you hit his head to stun him for a few seconds. Then, quickly run up to him, and perform a sneak kill to get the "Bloody Bar Brawl" achievement.