How can i get rid of belly fat quickly?

I’m 5’6″ and 113 lbs. I’ve gained a lot of belly fat lately because I’m in transition between sport seasons. I’ve not been exercising very much lately because i’ve been really busy, and my stomach which was pretty flat before isn’t really anymore. I’ve tried crunches and sit ups but its not working! I really don’t want it to get worse. Does anyone know any diets or exercises to get rid of belly fat? Thanks!