I've got a 5yo and 3yo and they won't ever tidy up after themselves. I've tried absolutely everything.
I've tried making into a fun game, I've tried helping them tidy up (which just turn into them sitting doing nothing while I do it all), I've tried consequences like "you can't do so and so before you clean up your toys" I've gotten so frustrated that I've threatened to throw all the toys away if they don't tidy up (I know, not exactly the best way to handle it). I've tried offering them something they like in return for tidying up, I've tried showing them how to do it, where things go, etc.
My 5yo especially just makes up excuses every time "I'm tired" so I tell her she either tidies up or goes to bed, and then she's suddenly not tired but still won't tidy her toys. She's magically got a tummy ache every time, she just "can't", etc, the list goes on.
My 3yo just copies her sister and it's becoming a massive problem because my 5yo will not ever do anything she's told to do, even if it's something she'll actually enjoy.
What can I even do at this point? I can calmly ask and show them what to do 73736382 times and they won't ever do it. I get angry and they won't do it either, and if I tell them off they both laugh at me if I tell them off and don't take it seriously at all.