I recently heard someone say "Ich hab eh..." (I'm not sure what "eh" means or how to spell it, but I tried [kind of sounds like "ay" mixed with "eh"]) "...keinen Hunger".
Does this convey a different meaning as opposed to "Ich hab keinen Hunger"?
If this particle is written it’s usually indeed spelled eh. It’s synonymous to longer ohnehin and sowieso, meaning ‘anyway’. In formal speech or writing, one of these should be used instead.
An English translation of the example sentence would thus be: “I’m not hungry anyway.”
PS: Also note that keinen often sounds like kein, but should still be written with the proper accusative ending.