What is the ruling on a student's cousin breaking his fast during the day in Ramadan due to the severe fatigue he experienced while taking an exam?

Your cousin is not permitted to break his fast unless he fears for his life, or the damage of one of his organs, or severe harm befalling his body. Mere fatigue does not permit breaking the fast. If he broke his fast without a valid excuse that permits it, he has committed a grave sin, and he must make up that day. No expiation (kaffarah (definition)) is required of him, because, according to the more sound opinion, it is only obligatory for breaking the fast through sexual intercourse.