Here's how you can understand it:
* Imagine a situation where someone is trying to be funny, but their joke falls flat. They might respond by saying something like, "Oh, that's hilarious. You really got me there," in a sardonically. Their tone would be sarcastic, almost mocking.
* Someone might say something sardonically about a politician's promises. They might be cynical, saying things like, "Oh, he's really going to fix everything? What a surprise!"
Think of it like a dry, sarcastic remark that cuts through the facade and points out the absurdity of something.