Help!: Increase sprint speed

Hi i'm 17 years old and would like to increase my sprint speed. I have always been a longer distance runner but nothing too serious. I would like to have increased speed to be able to play footy at a higher quality then i am playing at the moment. I currently try to run a 7-8k run every day but am finding it hard to fit in with my year 11 study's.

Any tips on exercise, diet etc. would be greatly appreciated