One idea could be that Naruto and Sasuke find a baby on one of their missions. They then have to figure out how to take care of it while also dealing with the political implications in the ninja world. Maybe the baby has some special power that attracts the attention of both friends and foes.
Another plot could be that a magical spell makes Naruto and Sasuke into babies themselves. Their friends have to deal with their infant - like selves, which would be really funny. Meanwhile, Naruto and Sasuke in baby form still have their strong personalities and try to communicate their thoughts and desires in the most comical ways.
Perhaps in this fanfiction, baby Sasuke and Naruto are accidentally sent to a parallel dimension. In this dimension, the ninja world is very different. They have to rely on each other more than ever to survive and find a way back home. Along the way, they meet alternate versions of their friends and foes.
One interesting plot could be baby Naruto and baby Sasuke getting lost in the forest together. They have to rely on their budding instincts and nascent chakra to find their way back. Maybe they encounter some small, friendly forest creatures that help them. Another idea is that they accidentally switch places in the village for a day. This leads to chaos as the villagers react differently to them being in the wrong 'homes'.
One plot idea could be that in the modern world, Naruto and Sasuke have to raise baby Naruto together. Maybe they're in a world where ninjas are like a secret society within modern society. They struggle to keep baby Naruto's identity a secret while also dealing with their own past traumas and how to pass on their ninja skills in a world full of technology.
Another idea is that baby Sasuke and Naruto are found together by a third party, like a wandering ninja who decides to train them both from a very young age. This would create a different dynamic as they grow up together with a unique set of skills taught by this unknown mentor. They would probably have a stronger bond from the start compared to in the original story.
One idea could be that Naruto and Sasuke find a mysterious baby in the forest. They then have to figure out where the baby came from and how to take care of it together. This could lead to some comical moments as they struggle with diaper changing and feeding.
A really interesting plot could be that Sasuke, for some mysterious reason, is the only one who can understand baby Naruto's unique needs. Maybe Naruto has some sort of power that only Sasuke can detect as a baby. So Sasuke becomes Naruto's guardian and mentor right from the start. As Naruto grows, they form an unbreakable bond that is different from their relationship in the original series. This could lead to many new adventures and challenges for both of them, and also change the way the other characters in the Naruto world view their relationship.
One idea could be that the baby has some unique powers inherited from both Naruko and Sasuke. For example, the ability to control both fire and wind in a new and unexpected way. This could lead to various adventures as they try to protect the baby from those who might want to use its power for evil.
Perhaps the baby has an unexpected connection to an ancient prophecy. Sasuke and Naruko then have to figure out what this means for their family and the Hidden Leaf Village. They might also face challenges from within the village as some people are suspicious of the baby's power.
One plot idea could be Sasuke discovers a way to travel back in time and meets baby Itachi. He then tries to protect Itachi from the future tragedies that he knows will occur. Another could be in a parallel universe where Sasuke is tasked with taking care of baby Itachi and he has to learn how to be a caretaker while also dealing with his own emotional turmoil. Maybe there could also be a plot where an enemy targets baby Itachi and Sasuke has to use all his skills to keep him safe.
A great plot idea could be that the baby has some sort of special power that no one has seen before. It causes both excitement and fear in the village. Sasuke and Sakura have to protect their baby from those who might want to use the baby's power for their own gain.