A fanfiction idea could be that without his glasses, Harry's world becomes a bit of a blur. He starts to rely more on his other senses. In the Forbidden Forest, this could be both dangerous and enlightening. He might be more attuned to the sounds and smells of the forest, but at the same time, he could easily walk into a dangerous area. His friends, Hermione and Ron, would have to be extra vigilant in protecting him. This new dynamic could change the relationships between them and lead to new adventures.
Well, perhaps Harry gets his glasses broken during a battle with Death Eaters. In this disordered world without his clear vision, he has to use his magic in different ways. He might use a spell to enhance his other senses, like a super - hearing spell. This would allow him to detect approaching enemies, but it also makes him more sensitive to all the noises in Hogwarts, which can be overwhelming. And he would have to rely on his friends even more to get around and complete tasks.
One possibility could be that in this fanfiction, Harry's glasses are some sort of magical anchor. Without them, he might accidentally slip into a different dimension. Maybe he was in the middle of a battle at Hogwarts, his glasses got knocked off, and suddenly he vanished. It could be that the glasses were enchanted by Dumbledore long ago to keep Harry in the 'right' magical space, and without them, he's lost in a sort of limbo.
Perhaps in the fanfiction, Harry discovers a new spell or a magical item that can temporarily enhance his vision without glasses. But there could be a catch, like it only works for a short time or has some side - effects. This would lead to a whole adventure of him trying to find a more permanent solution while also dealing with the normal challenges in the wizarding world.
His magic might be a bit off. Since he can't see clearly without his glasses and is drunk, his concentration would be severely affected. Magic often requires focus, so he might accidentally cast spells wrong. For example, he could try to cast a levitation spell on an object but end up making it explode instead.
Perhaps in this fanfiction, Harry is in a cage as part of a magical experiment. Some rogue wizards are trying to study how a wizard's magic is affected without their usual aids, like Harry's glasses. In the cage, Harry discovers new aspects of his magic that he didn't know before. He could start to manipulate the magical energy around him in different ways, even without clear vision, and eventually break free from the cage and confront those who put him there.
One interesting fanfiction could be where Harry discovers a spell that temporarily changes his eyesight so he doesn't need glasses. This could lead to all sorts of new adventures as he no longer has to worry about his glasses getting broken during Quidditch or in a fight. He might even be able to use this new ability to his advantage in his battles against Voldemort.
In this fanfiction, Harry without his glasses could be in a situation where he is forced to rely on his friends more when dealing with Horcruxes. His vision impairment without glasses makes it difficult for him to be as independent as he used to be. So, Hermione and Ron play a more crucial role. For example, when they are searching for a Horcrux in a dark and dangerous place, Harry has to trust their descriptions completely. And as they progress, Harry discovers that the Horcruxes are affecting his vision in a magical way, and he has to find a way to break this spell while still trying to destroy the Horcruxes.
Well, without his glasses, Harry might rely more on his other senses. His magical instincts could be heightened. When dealing with the Snatchers, this could mean he'd be able to sense their dark magic more acutely. He could use this to his advantage, perhaps by using magic to disrupt their search for him. And the Snatchers might underestimate him because they think he's at a disadvantage without his glasses.
One possible plot could be that Harry, without his glasses and drunk, stumbles around Hogwarts in a daze. He might accidentally end up in a restricted area, like the Forbidden Forest. Maybe he has some misadventures with the magical creatures there, all while being in a drunken state and unable to see clearly. His friends would then have to go and find him.
The plot could involve Harry using his magic in a different way. Since he can't see clearly, he might have to focus more on wandless magic or non - visual spells. For example, he could be trying to sense the magical energy in the cell to find weak points in the walls or barriers. And perhaps there are other prisoners in the cell with him who he has to interact with, and without his glasses, misidentifying them at first could lead to some interesting plot twists.