This is as simple as a cloud illusion can get. You don't need anything specific and just a little cloud hanging in the sky in front of you. Next you need a camera and someone who can click a nice picture and can guide you with the position of your mouth and hand. What you see here is just a play of perspective. Since, the man is close to the camera, the cloud appears to be a tiny object which as per his gesture, he is trying to eat.