Yes, there are some out there. You can start by looking on fanfiction websites like FanFiction.net or Archive of Our Own. However, the concept of Snape smacking Harry might be a bit controversial in the Harry Potter fandom as Snape is a complex character and such a violent act towards a student goes against the general spirit of Hogwarts, but some fanfictions might explore it in an interesting way within an alternate storyline.
Maybe in a fanfiction, Harry could be framed for something he didn't do, and Snape, believing the false accusations, smacks him in a moment of anger. This could then lead to a series of events where Harry tries to prove his innocence and Snape has to come to terms with his hasty action. Another plotline could be that Snape is under the influence of a dark spell that makes him act out of character, and Harry just happens to be in the wrong place at the wrong time and gets smacked.
Another way Snape could comfort Harry is by standing up for him in certain situations. Maybe when other teachers or students are being unfair to Harry, Snape steps in and defends him. This act of protection can be a great source of comfort for Harry, as it shows that someone is on his side even if they have had a rocky relationship in the past.
In some fanfictions, Snape might use his advanced knowledge of potions to brew a special healing elixir for Harry. He could also use his magic skills, like a complex spell specifically designed to mend Harry's wounds, whether they are physical or emotional.
Sure, the Harry Potter fandom is huge and full of creativity. Writers might come up with a story where Harry is Snape's master for various reasons. It could be due to a prophecy or a magical bond that no one expected. In this kind of fanfiction, we might see Snape having to follow Harry's orders, which would be a complete reversal of their normal relationship in the original series. This could lead to some very intense and dramatic storylines.
One possibility could be that in this fanfiction, Snape takes Harry for some sort of training or protection. Maybe Snape realizes that Harry is in greater danger than Dumbledore anticipates and decides to take matters into his own hands. He might take Harry to a secret location to teach him advanced magic or to keep him away from the prying eyes of Voldemort's followers.
In fanfiction, Snape teaching Harry Occlumency is often a very intense and complex relationship. Snape's own mixed feelings towards Harry add layers of drama. His strict teaching methods sometimes seem cruel but are also necessary to force Harry to master Occlumency. Harry, on the other hand, is often resistant at first, not fully understanding the importance and also being put off by Snape's attitude.
Snape is always complex. In this situation, he would be conflicted. On one hand, he has his long - standing dislike for Harry (or rather, his connection to James). On the other hand, as a teacher, he has a duty to take care of a student in distress. Drunk Harry would be a bit clumsy and giggly perhaps. His judgment would be clouded, and he might see Snape in a different light, not as the enemy but as someone who could help him, which could start to shift their relationship dynamic in the fanfiction.
Snape could also use his magical abilities in a more emotional sense. He might share his own past traumas with Harry, creating a bond of understanding that starts to heal Harry's broken spirit. By being vulnerable himself, he shows Harry that it's possible to move past pain.
Another reason might be that Harry is suspected of sneaking around in areas where he's not supposed to be. Snape, as a vigilant teacher, may punish Harry to maintain discipline in the school. He may think Harry is up to something related to the ongoing dangerous situations in the wizarding world and wants to keep him in line.