Well, it really depends on how the author writes the fanfiction. Some might make Sakura choose Itachi. Maybe because Itachi shows her a different side of himself during the fight, like a more vulnerable or understanding side that makes Sakura see him in a new light and fall for him instead.
In many fanfictions, Sakura might choose Sasuke. They have a long - established relationship, with Sasuke being someone she has loved since childhood. Her feelings for him are deep - rooted and often in fan - created stories, she remains loyal to those initial feelings.
However, there could also be fanfictions where Sakura doesn't choose either of them. She might realize that the fight between them is childish or that she doesn't want to be a prize in their battle. Instead, she could focus on her own growth as a ninja and decide to be independent.
Maybe it's about protecting Sakura. Itachi might think that Sasuke isn't the right person for Sakura and wants to protect her from Sasuke's darker side. And Sasuke, on the other hand, believes he can protect Sakura better than Itachi and that Itachi has no right to interfere.
Well, Naruto has a very warm and persistent personality. He's always there for his friends, and he has a big heart. In fanfiction, Sakura might see these qualities in Naruto and realize his true value. He's the kind of person who can make her laugh and feel safe, which could be very appealing compared to Sasuke's more brooding nature.
It could end with a draw. They both realize that they are equally matched and that their fight is not really getting them anywhere. They might then decide to have a more civilized conversation to resolve their differences.
I think Sakura would win. She's shown time and time again that she can hold her own in a fight. She's trained with Tsunade and has some serious punch - power. Hinata is strong too, but Sakura has more of an aggressive fighting style that would probably overpower Hinata in a direct fight within the context of fanfiction.
Itachi. He was a highly skilled and intelligent shinobi. His Sharingan abilities were extremely powerful, and he had a lot of combat experience. He also had a strategic mind, which would give him an edge in a fight over Naruto.
Sakura might be heartbroken at first. She has always been in love with Sasuke and to find out he's cheating would shatter her world. She could become withdrawn and focus more on her medical ninjutsu as a way to cope.
Sakura would probably be angry at herself for being captured. She's a proud ninja. So she would start looking for weaknesses in Itachi's hold on her. Maybe she would try to engage him in conversation to find out his motives, all the while formulating a plan to break free. She could also try to send out some sort of signal to her comrades if possible.
There would be other fans who might be intrigued. They like to explore different 'what - if' scenarios in fanfiction. They would see it as a creative way to explore the characters in a new light, even if it goes against the canon. However, they would also be aware that it's just a fictional alternative and not the real Naruto story.
Sakura would be over the moon. She would blush deeply and look at Sasuke with so much love in her eyes. She might be at a loss for words for a moment, but then she would find her voice and tell Sasuke that she has been waiting for this moment her whole life. She would also feel a sense of pride that Sasuke has chosen her, after all they have been through. And she would immediately start thinking about how to share the good news with their friends, especially Naruto, who has been like a brother to her and has also been a part of their journey.
Sakura might be initially frustrated. She's used to Sasuke being in control, so seeing him drunk could be a bit of a shock. But then she'd probably feel a sense of protectiveness and try to sober him up.