Put it at the peak of the surprise, then follow with the Awkward Moment Sound Effect to stretch the embarrassment, or the Womp Womp Fail Sound when the moment turns into a clear defeat. Keep it as the first reaction in a short sequence, before any punchline sound takes over the edit.
About this sound
This is a very brief Korean vocal gasp, built around the exclamation 뜨헉, romanized as ddeuheog, and lasting just over a second. It hits like a sudden intake of breath when something catches the speaker off guard. The effect is comic and jolting, turning a small surprise into an awkward, dramatic beat. The word itself is a familiar Korean shorthand for startled shock in chats and captions.