I read this story about 2 years ago. It was a fan-made and it told the story about Annie Cresta's victory in the 70th Hunger games.
I realize it's not a lot, but the things I remember from it are the things that are already mentioned in the books.
Annie was allied with the boy from her district who got beheaded. She won because the arena was flooded, and being raised in district 4, she could swim better than the kids from other districts.
The writer created the story with the little information they got in the book in a very interesting way, telling the whole story before the game (reaping, being mentored by Finnick) and during the games.