Unlike the rest of the Gaang, Sokka’s Fire Nation outfit is almost entirely Chinese-inspired. The capelet he’s wearing is inspired by “cloud collars” or Yunjian (云肩).
The shirt he wears is a long, sleeveless Tangzhuang (唐装). Zuko also wears one in Season 1. As a side note, I just love frog clasps, they’re so elegant.
The five cutest, most wholesome characters in Hazbin Hotel will still look utterly terrifying the moment you are threatening their loved ones (or you're in stabbing range, in Niffty's case).