This is the 13756th most frequent Korean word.
마시던
"마시던" means "that was being drunk" or "that one used to drink."
In this sentence, '마시던' is used to describe the coffee that I had been drinking before.
나는 내가 마시던 커피를 다시 마셨다.
I drank the coffee I was drinking again.
Here, '마시던' refers to the tea that I was previously drinking and had not finished.
마시던 차를 책상 위에 두고 잠시 자리를 비웠다.
I left the tea I was drinking on the desk and stepped away for a moment.
'마시던' is utilized to indicate the juice that the friend was in the process of drinking or had been drinking before.