This research project aimed to determine the optimum rehydration fluid for 16-18 year old female athletes after high intensity exercise. 12 participants provided urine samples before and after exercise and were given one of four drinks to consume. Urine samples were compared to a chart and given values. The results were inconclusive as no clear optimum hydration fuel emerged. However, it showed individuals should test themselves to find their own optimum fuel as rehydration needs vary. The report included the research process, data collection and analysis methods, and results. Areas for improvement included ensuring all participants worked equally hard and using more precise measurement tools. Future recommendations included testing different populations like males or less fit athletes.