In some fanfictions, it could be that Sakura is under a genjutsu (illusion technique). The genjutsu makes her act in ways that seem like she is cheating on Sasuke. She doesn't realize what she is doing until it's almost too late, and Sasuke has to figure out what is really going on to save their relationship.
One possible plotline could be that Sasuke, feeling conflicted by his past and the secrets he holds, distances himself from Sakura and starts to develop an inappropriate emotional connection with someone else, which Sakura misinterprets as cheating. As for Itachi's role, perhaps his memories or the influence he had on Sasuke play into Sasuke's actions, like Sasuke trying to live up to some ideal Itachi had that made him question his relationship with Sakura.
A possible plotline could be that they are both on a mission to rescue their kidnapped comrades. They have to work together, using their unique ninja skills. Female Sasuke with her lightning - fast attacks and Sakura with her super - strong punches.
One possible plotline could be that Sakura is physically held by Sasuke against her will, and she struggles to break free while also dealing with her complex feelings for him. Maybe she's trying to understand his motives for holding her in such a way.
Well, perhaps Sasuke has to leave the village again for some mission or his own personal vendetta. He doesn't explain his reasons fully to Sakura, and she feels abandoned once more, which makes her cry. In a different scenario, Sasuke might be in a battle where he has to make a tough decision that involves sacrificing something that Sakura holds dear. When she realizes what he's done, she's heartbroken and cries. Or it could be that Sasuke is training extremely hard and pushing himself to the limit. Sakura is worried about him, but when she tries to stop him, he dismisses her concerns harshly, reducing her to tears.
One possible plotline could be that Sasuke is under some sort of dark magic or mind control when he binds Sakura with snakes. Maybe an enemy has manipulated him into doing this as part of a larger scheme against the Hidden Leaf Village. And Sakura, being the strong - willed kunoichi she is, tries to break free and also reach out to the real Sasuke within his mind - controlled state.
Perhaps Sasuke uses Sakura to get closer to some information. He might know that Sakura has connections or knowledge that can help him in his quest for revenge or for protecting the village. So he uses her in a strategic way while she is initially unaware of his motives. As the story progresses, their relationship could develop in complex ways.
One possible plotline could be that after Sasuke has finally returned to the village and reconciled with Sakura, they start to rebuild their relationship. They go on dates, share their feelings and experiences during their time apart, and gradually their love deepens until they reach a point of expressing their physical love for each other.
I'm not really into the idea of Sasuke and Sakura cheating fanfictions as it goes against the essence of their relationship in the original Naruto series. However, you can try searching on some fanfiction websites like FanFiction.net or Archive of Our Own. They might have some stories related to this, but keep in mind that these are often not in line with the positive portrayal of the characters in the official story.
One possible plotline could be that it's part of a training exercise gone wrong. Sasuke, in his overzealous attempt to train Sakura, ties her up to test her escape skills. Another could be that they are in a dangerous situation where Sasuke has to restrain Sakura to keep her safe from an unseen enemy. Maybe they are in a magical or cursed area where Sakura's movements need to be restricted for a while.
Another plotline could be centered around Sasuke's ninja duties. He might be constantly away on dangerous missions, and when he's home, he's so preoccupied with the safety of the village and potential threats that he neglects Sakura's emotional needs. This could lead to a situation where Sakura feels unloved and Sasuke seems to 'hate' their married situation because he can't balance his two worlds well.