If I remember correctly, then the punishment is that he will never reach the top. However he is retrying it on his own will because he believes that he'll reach it this time for sure.
If that is correct, then I guess my answer would be anti addiction therapy 🤔
By becoming a Buddhist he can stop his own suffering, rendering the punishment no longer a punishment even if he continues to roll the boulder for eternity.
Get 2 smaller stones. Put them down in front of the boulder. As you push the boulder up, kick the stones along with it, so that the stones would hold the boulder in place for you.
Get to the top, and get hit by lightning from angry gods for your impudence.
He should accept that there are some things in life we can't change and just brace himself against the rock. He won't escape the burden but refusing to push against the rock will lighten his load.
There’s this mountain of pure diamond. It takes an hour to climb it, and an hour to go around it. Every hundred years, a little bird comes. It sharpens its beak on the diamond mountain. And when the entire mountain is chiseled away, the first second of eternity will have passed.
Hades: Your punishment is to push this rock up a hill. However before you reach the top, it will roll down the hill. You will do this for eternity! Bwahahaha!
Sisyphus: Nope.
Hades: What do you mean "nope"?
Sisyphus: Nope. Fuck your rock. Fuck your hill. Ain't doing shit.
After a brief search I can't find any mention of any punishment for Sisyphus if he stopped pushing the boulder up the hill. That said, this is all taking place in Tartarus so there probably isn't much else to do and endlessly push a boulder up hill might be the better option lol. I can relate.
He could convince the gods that they must imagine him happy. Then they'd figure that he's just as miserable pushing the rock as he would be not pushing the rock, so they let him free. Or maybe they give him an even more miserable punishment.