If sorry is replied by "you better be sorry" than what does it mean?
The correct response in English is "You had better be sorry." or "You'd better be sorry.". This is an angry response which is sometimes aggressive and threatening.
For example, my friend spilled his drink on me and said "Sorry". I angrily responded, "You'd better be sorry, this shirt cost me 100 euros!"
However it is possible to use this expression as a joke between friends.