Well, one possibility could be that Itachi sees potential in Sakura's skills and decides to train her in the ways of the ANBU. He might start with teaching her stealth techniques, like how to move silently and blend into the shadows. This could involve a lot of practical exercises in different terrains.
She would become more stealthy and less impulsive. Since ANBU work requires a lot of secrecy and patience, Itachi's training would force her to change her approach. She might start thinking more strategically and be less likely to jump into a fight without a plan. This could completely transform her from the somewhat brash character she was before.
It could be about Itachi training Sakura in various skills, like ninja techniques. Maybe Itachi imparts his knowledge of genjutsu or combat strategies to Sakura.
You can try looking on fanfiction websites like FanFiction.net or Archive of Our Own. They have a large collection of Naruto - related fanfics, and there's a good chance you'll find the 'itachi trains sakura' one there.
One possible plot could be a story where Sakura, Itachi, and Shisui are all part of the ANBU. Itachi and Shisui could be mentoring Sakura in the ways of the ANBU. They might go on a dangerous mission together, facing powerful enemies. Shisui could use his unique abilities like Kotoamatsukami to gain an advantage, while Itachi's Sharingan and combat skills are also crucial. Sakura, with her medical ninjutsu and growing combat skills, could prove to be a valuable asset in the team.
She probably changes in her mindset. Itachi's influence might make her think more strategically. Instead of just relying on brute force or basic medical ninjutsu, she could start to analyze situations better and come up with more effective solutions. For instance, she might learn from Itachi how to anticipate an opponent's moves based on their body language and chakra flow.
The main characters are obviously Itachi and Sakura. Itachi is a complex character from the Uchiha clan known for his powerful Sharingan abilities. Sakura, on the other hand, is a skilled kunoichi who has grown in her medical and combat abilities. In this fanfiction, they are usually placed in the context of the ANBU, which is a special and secretive part of the ninja world.
One possible fanfiction could be about Sakura joining an Anbu team that has Itachi and Shisui. Maybe Sakura is a new recruit and she has to learn from the two experienced shinobi. Itachi could be the calm and collected leader, while Shisui is the more easy - going one who helps Sakura adjust to the harsh Anbu lifestyle.
There is a fanfic called 'Itachi and Sakura: Anbu Allies'. It delves deep into their Anbu experiences. The author does a wonderful job of depicting the Anbu world and how Sakura and Itachi's skills complement each other. It also has a great plot that keeps you hooked from start to finish.
Sakura would likely develop her combat skills further. In the ANBU environment, she would face more dangerous opponents, which would force her to become more strategic. Itachi, already a complex character, might show more of his internal struggle between his loyalty to the village and his love for his family. Shisui could develop in terms of his leadership skills, as he and Itachi might lead Sakura in missions. He could also become more jaded as he faces the darker side of the ninja world.