I used to play sport at a high level and one of our team members was Muslim. We had a weekend training camp during Ramadan and although we were doing some pretty intensive training, she didn't take water or food during the day. One day, she got lightheaded and almost fainted and the coach made her sit out for the rest of the session, but she still didn't want to take water. I think there are circumstances when people can break fast, but for her this hadn't reached that point yet.