It could be that the sweatshirt has some special significance. Say it was a gift from a very important person or it represents a memorable event. So when it comes to that particular sweatshirt, there's no more to be said, it's just 'end of story'.
Sadly, I have no idea who the creator of the 'brittberry dance camo fanfic' is. It could be a new writer in a niche fanfic community. They might have been inspired by a particular event, a dream, or just their own imagination. Since fanfic is often a creative outlet for fans, it could be that this person just wanted to share their unique vision of 'brittberry' in a dance - camo - related story with others in their community.
Well, without having read it, it could be a fan - created story that combines the elements of 'brittberry' (maybe a character or a person), dance (so perhaps there are dance scenes described), and camo (which could be related to a military or outdoorsy camo pattern). It could be a fun, creative piece that the author uses to explore different scenarios or relationships within this odd combination of elements.
Since I've not come across 'Britberry Fance Camo Fanfic' before, I can only speculate. It might be a fan - written story that features a character named Britberry in a fictional place or situation that has some connection to 'Fance' (whatever that might be) and also incorporates camo elements. For example, perhaps Britberry is a soldier or adventurer in a world inspired by Fance and has to use camo to achieve certain goals in the story. It could also be a more creative and abstract take where these terms are used symbolically rather than literally.