Dude. Please realize that the pressure in a planet is nothing compared to the gravitational pressure in the sun.

Dudette. Rationalize how mighty and invulnerable, or at least regenerating, The Hulk is.

The core of the sun is 150,000,000K. That would kill him. Literally your brain would be gone before he even reached the core and the gravitational pull wouldn't allow him to escape. Regenerating is useless when your brain is gone along with your body.

His skin would protect all his organs. It's the reason those well placed shots to the head and heart didn't end his comic when it started.

You can't fucking swim in a damn star. There is no liquids in a star. It is a ball of burning gas. Literally he can't win.

He can use it's gas to propel himself, much like how people skydiving move. He would rocket himself back and forth through the burning suffering gas, until he had the momentum to escape the gravitational field. You don't literally understand, Hulk can not die.

Plus if we want to be technical, show me the number of times Superman has actually thrown anyone into the sun. He fought doomsday, only pile drived him. He fought Darkseid, only kicked him into a portal. He fought the Elite and pretended to be evil, even then he didn't throw anyone into the sun.

Now if Superman is a God in this fight, and the Hulk is mixed in this fight, Hulk will use Banner's knowledge and bring a kryptonite war glove. Problem solved!