Jannik Sinner stormed into the third round of the Australian Open with a dominant win against Jesper de Jong.

The Italian fourth seed took just 103 minutes to thrash the Dutch qualifier 6-2 6-2 6-2 under a closed roof on Margaret Court Arena on a rainy day.

Sinner, 22, who will face Daniel Elahi Galan or Sebastian Baez in the next round, said he has been working in the gym on his off-days in Melbourne.

He joked he wanted a muscular physique like the actors in TV show Baywatch.

"Tomorrow I have a day off, trying to practice myself into the match rhythm. I [will do] also a little bit gym. Even if you can't see it, I'm skinny, but it's OK," Sinner said.

"I'm happy with my physicality at the moment. Of course it's a dream to have the 'Baywatch' physicality but it's OK."

Elsewhere, Australian 10th seed Alex de Minaur swept aside Italy's Matteo Arnaldi 6-3 6-0 6-3.

Defending champion Novak Djokovic will be up against Australia's Alexei Popyrin in Wednesday's evening session on Rod Laver Arena.