Eric's heartbeat picked up some at the offer. It insinuated that John knew what he was...but, it couldn't be. The vampire couldn't have any idea, not now. The offer had to be a reflex, an act in response to being caught in the moment. Eric shook his head and made a face, "No, blood isn't my thing. You take all you want."
In spite of declining the offer, part of Eric did want the blood. He wanted to feast with John, to share something so delicate and intimate between them that such an offer came with. But that would mean exposure, and he couldn't risk losing Macklyn again. Not for anything.
He approached John slowly, aware that his friend was in high spirits fresh from the kill. "When you're done we can go to the studio if you want." He was trying to lighten the air, trying to coax his friend back to the level of civility.