I shouldn't have drunk alcohol on an empty stomach.
빈속에 술을 먹지 말았어야 했는데.
[영어식 어순 익히기]
I shouldn't have drunk alcohol / on an empty stomach.
나는 술을 먹지 말았어야 했는데 / 빈속에
[should have PP : ~했어야 했는데 / shouldn't have PP : ~하지 말았어야 했는데]