what does this comment mean? genuine answers please..?

[c_kayak_fun]

Since you don't tell us EXACTLY what you said to the co-worker it is impossible to interpret precisely what their response might have meant. Saying something is "a slap in the face" can mean the person takes it as an insult but in some cases it is more benign, as in that it is a "wake-up call" or something that snaps you out of being groggy . My guess is that is what he meant: the coffee was an energizer for him, like you are (meaning that there is something energizing and upbeat about you that helps him wake up, like the coffee does.

I would suggest instead of brooding and perseverating about their comment, you just forget about it, since you get along fine with the guy and he seems pleasant to you.

Often people just misinterpret what you say and it is nobody's fault. For instance, my boyfriend, who is a doctor, saw a notice by a friend of his on Facebook that she had arranged for her husband with cancer to be treated at a special out of town clinic. He posted a note asking her "I'm curious as to why you decided to do that. What do they offer there that you could not get at the local hospital?" What he meant was that he was honestly curious about the kind of treatments that were available at the special clinic and how they might help her husband. But she took it completely wrong and thought that he was getting down on her for going out of town instead of the local hospital. She responded in an angry and indignant way and then blocked him so now he can't even try to explain that she misunderstood what he was saying.

It is usually best when someone makes a comment that strikes us an odd, out of place or insulting, to presume that they spoke accidentally or you heard it wrong. If there has been no pattern of hostlity or insult from the person before or since, it was almost always just a slip of the tongue that means nothing.