Possibly the most important phrase in the Korean language, especially if you add "bap" before "sa-ju-se-yo" (oppa, buy me FOOD)
Here's how you say it:
오빠 이것 사주세요!
Oppa, igeot sa juseyo
Literally - Oppa, this, buy please.
What it means - Oppa buy this for me, please!