Many would liken Samantha Stosur’s fourth-round challenge at the French Open to taking candy from a baby.

But not Sloane Stephens, the 19-year-old sweet tooth who has already cut the candy to emerge as the surprise packet of the championships.

Stephens, set to be the youngest player in the world’s top 75 after her unexpected run at Roland Garros, will tackle Stosur on Sunday as the most improved player on tour.

And there was no sugar-coating from the fearless and fat-free teenager when she was asked for the secret recipe to her surprise success.

“I stopped drinking soda. I think that helped me. I haven’t eaten as much candy,” Stephens said.

“Oh, my God, I was drinking Fantas like twice a day.

“Then like dinner was really late, so I would go and get one before I left and then I’d drink another one and I was like ‘whoa, that’s a lot of sugar’.

“So I stopped doing that. I was having brain farts and I don’t know what I was doing.

“I was being 19 and I think now I am being 29 … I’m moving in the right direction, I think.”

Growing up off court and on, Stephens has reached the last 16 without conceding a set, having never previously won a match in Paris.

Inspired by Serena and Venus Williams, the African-American says it’s “kinda weird” to be still in the draw when her idols aren’t.

“Now I’m going to have more Twitter followers. That’s good,” the funky youngster said.

“I mean, it’s always good to be noticed and recognised for sport. I think being up there with Venus and Serena, I mean, that’s awesome.”

Pre-tournament, Stephens considered a successful campaign would be “definitely going home first class”.

That she can now do, with a guaranteed 80,000 euros ($A102,500) prize money, at least, heading her way.

“But mum won’t let me buy a car,” she said. “Can someone please talk to my mum.”

A shock win over Stosur – and another 75,000 euros ($A95,000) in the bank – and Mrs Stephens could hardly say no.