1. What does it mean?
카페인 수혈 literally says caffeine transfusion. It exaggerates grabbing coffee or another caffeinated drink to feel more awake, treating an ordinary drink as an urgent replenishment.
Also written or said as kapein suhyeol
2. The nuance
It is figurative, not an actual transfusion or medical advice. The joke does not mean more caffeine is always better or that it replaces rest.
3. Examples
“친구가 카페인 수혈하러 간다며 커피를 사 왔어.”
My friend said they were going for a caffeine refill and came back with coffee.
“카페인 수혈 얘기를 하다가 오늘은 그냥 쉬기로 했어.”
We joked about needing a caffeine infusion, then decided just to rest today.
Sources
References support the meaning and usage. Example sentences are written for NoCapWiki.