Place it right after the reveal in an edit, then follow it with Eww Brother Eww or Damn to extend the reaction. Use Oh My God Wow before it when the setup needs surprise first, so this clip becomes the payoff rather than the opening.
About this sound
This under-a-second clip is a single short vocal grunt, just the word 'guhh' delivered with a flat, unimpressed tone. It lands as a quick burst of disgust, confusion or weary disbelief, the kind of noise someone makes when words feel like too much effort. Its blunt, unpolished delivery makes it instantly recognisable as a reaction to something awkward, gross or plainly ridiculous.