<p>Definitely a stretch, but for any Futurama fan...</p>
>!It could be Slurm! <br>Here's a link with more info about it. <http://futurama.wikia.com/wiki/Slurm></br>
<p>I am a food you'd never find or certainly wouldn't eat</p>
>!Of course we can't find it because it's fictional, but even if it were real, I would never eat secretion from the anus of the Wormulon Queen
<p>I don't exist, and yet I do, now isn't that a feat!</p>
>!It doesn't really exist, but does exist in a fictional show
<p>I am a good example of something that is wrong</p>
>!Slurm is a good representation of real world soft drinks and show how corporations promote them even though they're addictive and bad for you
<p>I'm mentioned in the speech of some but more often heard in song.</p>
>!Slurm sounds like slur, which is something some people do when they talk, but usually slurring is intentionally done in songs.
<p>I know it's probably not the answer, but still, food for thought ;-)</p>