How do you say sorry when you want to be sorry? My sister and I don't have a good relationship and I really want to fix that. I always feel like a bully around her.

Saying you're sorry and changing your behavior to really show that you're sorry are two different things. It's great to apologize verbally, but follow it up by treating your sister better. First, do your best to stop bullying her. Use kind words, even when she lashes out at you. Do nice things for her, even when she doesn't appreciate it. It may take some time for your sister to realize that you want to fix the relationship, but it will have to start with you. When she does start to notice, your relationship will slowly begin to improve.