What's better to say to someone to apologize?

I think in the future, you should just stand up for what you believe in. Don't be afraid to disappoint friends.

Dont take sides between two friends in the future. I learned that the hard way. Dont ever gossip negatively about your friends. I would tell them look I shoulda stayed out of it. Good rule of thumb is to always think when youre opening your mouth to gossip "in private" "would I say this infront of him?"

I would say, apologize to both sides and say you didn't want to get in the middle of their arguments, so you aggreed with each party when you were with them. Say you're sorry and tell them to please not make you feel like they are putting you in the middle next time because you like/love them both.

I think it's possible that neither of these friendships is recoverable. From what you say, it sounds like there's a whole lot of fibbing, overblown drama and emotional immaturity going on with all three of you, and those things are the exact opposite of what's necessary for a friendship to recover from a spat. While I'm not sure about you, from what you say about the other two, they definitely sound like a couple of pair of toxic, immature bitches.

It seems to me the best you can do is consider all this a learning experience. For example, try to remember that unless you're talking about someone you're absolutely certain you'll never want to be on good terms with, never call someone "crazy"; if instead of saying that about ex-friend A to ex-friend B, you'd said something like, "I don't understand how she can think that", then ex-friend B would have felt you were validating her, but you would have left yourself an out with ex-friend A (assuming she's not a totally irrational loon).

Maybe the most important lesson is that you don't have to get involved in shit between friends. You have your relationship between each of them, and they have their relationships between each other. When there's a conflict between them, if you're not directly involved in the dispute and you're not clear on whose side you are, the sensible approach is to metaphorically back off and say it's something for them to sort out between themselves. The idea that you always have to decide who's right and who's wrong and pick a side is something you all should have left behind in high school (and probably even earlier).

Say “I’m sorry you made me do this”

I don't know that an apology is going to work. You come off as two faced either way.

More importantly is the learning experience. I guess my question is how did you really feel. Did you really agree with one and not the other? If so stay true to yourself and say that. If you didn't agree with either or saw good and bad in both sides then say that, and stay true to yourself. Which would have been a good time to say I'm not going to take sides and get in the middle.

If they decide not to be your friend because of your view or stance then it's their loss.

Water under the bridge at this point.

I would just tell them, not necessarily an apology, but that you felt trapped in the middle and you value both their friendships so you stupidity took both sides. I don't want to lose either of you as friends but I won't be put in the middle again.

It's time to grow a pair.

Please learn not to take sides. Learn to acknowledge things you feel are valid points (and both sides virtually always have valid points), and then after acknowledging a valid point you can say something like "have you considered that "X" also has a valid point (or points)?" and just pretty much exit the conversation at that point. It takes a bit of training and willpower... but, it works.