One possible reason could be that he's had a bad experience with the taste. Maybe the ramen was made wrong one day and it left a really bad impression on him.
One possible plot could be that Naruto makes a huge mess at the ramen place while training or showing off some new jutsu, and as a result, he gets banned. Then he has to find a way to make it up to the owner.
One possible reason could be that Naruto might feel Kakashi is too strict with his training. Maybe Kakashi's methods are too harsh for Naruto, making him frustrated and gradually developing dislike.
In the original story, Naruto loves ramen. It's a big part of his character. So in this fanfiction, it's a complete opposite. It changes the fundamental aspect of his relationship with food.
One possible reason could be jealousy. Maybe Naruto has some special abilities or a prophecy surrounding him that makes his family members, who might be less favored, jealous. For example, if there's a prophecy that Naruto will be the most powerful ninja in the village, his siblings or parents might envy that future for him and start to hate him out of their own insecurities.
Another reason might be related to their different ideologies within the ANBU. Naruto may have believed in a more collaborative and friendly approach within the organization, while Sasuke might have been more focused on individual achievement and power. This fundamental difference could lead to Naruto hating Sasuke in the fanfiction.
One possible reason could be that in the fanfiction, Kakashi might have made a decision during a mission that Naruto strongly disagreed with. For example, Kakashi could have chosen to sacrifice something important to Naruto in order to achieve the overall mission objective.
One possible reason could be jealousy. Maybe his brother has some special abilities or gets more attention that Naruto feels he should have. For example, if his brother is really good at a certain jutsu and is always praised for it while Naruto struggles, that could lead to resentment.
One possible plot could be that a new and mysterious ingredient is discovered in the Naruto world. This ingredient is added to the ramen in the shop, and it gives those who eat it special powers. Naruto and his friends then have to protect the ingredient from villains who want to use it for evil.
One possible plot could be that Naruto discovers a new secret ingredient for his favorite ramen. This ingredient could be a rare herb only found in a hidden part of the forest. He then tries to convince Teuchi, the ramen shop owner, to use it in the ramen. Along the way, he has to face off against some ninjas who also want the herb for their own purposes.
It could be a fanfiction that focuses on a character in Naruto experiencing withdrawal symptoms related to ramen. Maybe Naruto himself is deprived of his beloved ramen for some reason and the story explores how he copes.