"Yeah... <swallowing> ...we shouldn't have mixed <gulping> Jaeger and Wild Turk- <holding breath> Turkey"
"Eiiiw... You feelin' barfy?"
<nods slowly, eyes closed>
never a pleasant feeling.
I'll get around to doing that unpleasant chore when I'm not feeling so barfy.
I can't go out tonight: the thought of seeing him there makes me barfy.
How to use in a running sentence: "Look at that cute couple holding hands, kissing each other as the sun sets on the beach. Barf."
But actually, you are just jealous and would not actually mind being in said situation yourself.
Note that "barf" and "barfy" can be interchanged depending on your personal grammatical preferences.