Has he been too stealthy without even realizing it? Omi isn't sure what to make of the surprised look... and his mind is cloudy enough that he's not really coming up with alternative explanations. All he does catch on is that sort-of declining, maybe because he's embarrassed about the idea he seems like he's so broke he can't even afford a vending machine drink. Oops... Omi hadn't meant to insinuate that (even if it was one of the possibilities that floated through his mind).

"Ahh, sorry! I didn't mean it like that. I just felt like doing something nice... are you sure you won't let me?"

It's getting a little bit pushy, maybe... but he really wants that coffee!