Place it at the end of a refusal scene, after the request has been shown, then follow it with Awkward Moment to underline the reply, or lead into it with Anime Ahh when the scene needs a reaction first.
Über diesen Sound
A short anime voice clip repeats the Japanese refusal iya iya over just under six seconds, the words tumbling out in a hurried flustered rush that sounds like someone shaking their head while backing away from an awkward request. It feels playful and embarrassed rather than angry, a light comic no for moments that are too silly to refuse seriously.