What are some clever ideas that Sisyphus could use to escape his punishment?

Meta-answer: He really shouldn't. Using clever ideas to escape punishment was what caused him eternal punishment in the first place.

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.

Show the massive ball to Cerberus.

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.

Eventually, either the boulder or the hill will erode enough that the task will be trivial.

Just bang Hades already, and maybe Zeus, too

You believe in Bouldy, and Bouldy, he believes in you.

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.

Top of my head: chip away at the boulder and take it piece by piece

Perhaps some sort of wheelbarrow? Maybe a shovel to dig a hole to drop the boulder in so it doesn't keep rolling back down?

He should have asked how to do the rolling of boulders.

He missed his chance.