"You are correct. I didn't." Castiel wasn't being a smart ass, but rather stating a simple fact of the matter that he indeed, did not answer her question. Maybe because he wasn't sure how to answer it or maybe because he was afraid that his answer would finally make her take her leave of him for good. It wasn't something he truly wanted to acknowledge, but after she told him how unnatural this was for her, he had to admit that this was not something that likely came easily at all for her. It certainly didn't for him and he was the one who was newly human. He had yet to fully shake everything from when he'd been an angel, mostly out of the fact he'd always been an angel, until recently. That was all he knew. It was how he coped and dealt with things. This was entirely different for him.
"If I answer your question, you will give me whatever is in that bottle?" He tilted his head a little to the side, just trying to read the situation, although he only had his perception he was blessed with as a human. He didn't think she was lying, he had no reason to believe that, but he thought that was absurdly simple, for him to just give her an answer to her question and be allowed to feel better. "He really claimed that it would allow me to sleep peacefully?" It was a concept that appealed to him greatly, because as of right now, his sleep had been fitful because he'd been unable to breathe through his nose and it made it difficult to really sleep in a manner that was restful and revitalizing for him.