What best words should I give to my friends who just broke up?

Your friends? More than one friend broke up?

Do you mean you know them both, him and her?

Were they in a conflict when they broke up?

Do you want to say something to make them feel better?

Whatever the situation, it was between them. There is nothing that you need to say about that. But if you are close to them, you can ask if it still bothers them, and ask if there is something you can do to ease their worries. I wish I can give you a better advice.

You don't say anything unless they say something to you.