Even though they were going through the motions of flirting, and even though Sulu... well, even with Ianto sick as he was, Sulu still wanted to be intimate with him. But the fact was that Ianto was sick, and he looked sick, and after thinking for a few terrifying days that he would never so much as get to see Ianto again, he was honestly content enough to just take what he could for now. It didn't mean he didn't want to try and flirt with Ianto - it just felt cheap. He didn't feel like flirting. He felt like wrapping his arms around Ianto and never letting go.

So, he ignored the baiting and instead said, "It's not addictive, exactly. I definitely wouldn't say we should be drinking it every day, though." After all, it was something that made you feel good - and it was a well known fact that too much of a good thing could be bad.