Frequently said by people experiencing loopy, silly fits of laughter, "Cood" is simply Food with a C. And that's what's so funny!
Also can be used to describe skeevy, grody, dodgy, or otherwise distasteful things.
Girl: Ahahahaha!! Cood! It's like food, with a C!!! Ahahahah!!!
Jim: That girl was all over me last night. What a coody girl. Yeeeechhhh.