Ok, I got an answer. Like seriously!
Ever heard of Chimika Burger? It's a hole in a wall, by GuoGuang Rd., just opposite NCHU. You wouldn't guess by the outside, they have best ever burger. They just put some umbrellas out, and menu on the wall. Many types of burgers, I suggest the German style cheeseburger, but anything is awesome too. Quite cheap.
here's some photo and review: http://www.ipeen.com.tw/comment/190126- ... %ADCHIMIKA
Only problem: the guy doesn't open on Sundays, and often on very rainy days.
Forgot to say, they don't really have drinks, but don't mind if you buy then else and bring it.
I am no friend of the owner, I just truly enjoy their burgers, and want other to try, because I regret I didn't know this place before, even I studied in NCHU for 3 years!!