How do you say sorry in cantonese?

If you're writing "I'm sorry" in Chinese, it is 對不起 (Traditional). But in spoken form, it would take the form of "dui (duy) mm ju".

It's hard to explain through Words without audio, but the "ju" is like a mix between "Jake' and "Juke". Neither too much of an "a" sound, nor too much of an "u" sound.