You Can't! 

Posh upper class English way of saying, You Cunt!

Oh no you caaaant! The upper class lengthen their A sound.
Female horse rider shouted it out to me as I slowed my lorry as I passed and the air brakes hissed. She shouted it out just as her horse bolted.
And for a moment, puzzled, I thought why did she shout out 'You Can't!'

You Can't! by shakespeare9 December 26, 2011

You can't sit on your own arse. 

An English idiom demonstrating the fact that one cannot sit on one's own arse.

Well, you know what they say; "You can't sit on your own arse."

You can't sit on your own arse. by Someone from Bremen. December 19, 2022

You can't win for losing 

When you win something but , winning means you lose either psychologically emotionally physically financially, anyway that negatively impacts you.

You do the dishes cuz your parents told you to and ,then when you're finished they yell at you for doing it wrong even though they didn't tell you how to do it in the first place ! Man you can't win for losing

You can't win for losing by dragonboy8586 October 15, 2019

You can’t turn a hoe into a housewife

If you’re with a girl and she acts a certain way or does certain thing like gold dig, thot around, etc. then you cannot make her into someone who will treat you right and with respect. In short, avoid THOTS!

“Man I love Kiana but she out here entertaining these other dudes. What do I do?”

“Well you know the old saying my man’s ‘you can’t turn a hoe into a housewife?”

You can’t turn a hoe into a housewife by BigSlickDaddy April 27, 2022

You can't polish a turd

You can't make something that's not naturally good great even with the hardest attempts.

"After years, he's just never going to change his selfish ways." "Well, you can't polish a turd!!"

You can't polish a turd by SarcasticSeminar101 August 3, 2015

You can't make this stuff up 

An expression said in response to an an unbelievable fact or piece of news.

Did you hear about that burglar who called 911 after breaking through a store window because he was afraid he'd cut himself on the way out? You can't make this stuff up.

You can't make this stuff up by barcos August 11, 2012

you can't be just a little bit pregnant 

It means that the situation that is being described is a binary. It is something that is either IS or ISN'T. Such as is the case when one is pregnant. One either "is" pregnant or "is not", there is no in between or partial pregnancy. It means it is a situation in which there is no ambiguity or no gray area. You can't be "just a little bit" of certain things.

You can't be just a little bit pregnant when you are talking bankruptcy. You can't be just a little bit bankrupt. You are either bankrupt or not bankrupt.

References:
Lou Mannheim (Hal Holbrook) in the movie "Wall Street" used this phrase while conversing with Bud Fox

you can't be just a little bit pregnant by idiomsfanatic April 13, 2007