Does anyone have a good idiom for when someone asks you to guess what they are doing/thinking but you are not interested in making an effort to guess? [closed]

It's not an idiom really, but you can always say "I give up". What's nice about this is that it's polite and non-confrontational.

For example:

"[...] Guess what?"
"I give up?"
_{Alien Ice}

“Well, guess who I met there?”
“I give up.”
“Russell Canton.”
_{Why Did She Have to Die?}

Not much of an idiom, but perhaps "I'm in no mood for games."?

I usually say "Can't be arsed", but again that's not an idiom.

Edit: I've just been corrected. It indeed is an idiom! Sorry, my bad

"I don't know, what?" (Insert when, who, why, where as appropriate).

This usually cuts the guessing short and gets straight to the question without being rude, and also acknowledging that you are unable to guess, which may well be why the question is asked in the first place.