The dare is for Katara to act like Azula and it's from avatar11toph.

Katara: What? I absolutely hate her!

Azula: I hate you, too! And how is she supposed to act like me?

Katara: I guess I can act out when I chained her to where that water was.

Ali: Sure. I think that is fine.

*Katara acts out that scene.*

Ali: Is that good avatar11toph?