Coconut water is a good thirst quencher and source of rehydration. It contains electrolytes such as potassium, sodium and magnesium, but it also contains fructose and glucose, albeit in lesser quantities than in other fruit juices.
For rehydration during high intensity exercise, coconut water is comparable to sports drinks because it also helps replace fluids and electrolytes lost through sweat.
What sets fresh coconut water apart from sports drinks is that it is free of added sugars. On the other hand, packaged coconut water often has some added sugars. Hence, be sure to check the list of ingredients first.
If you are trying to limit your sodium intake, drinking plain water is your best hydration choice. This will also help you avoid consuming unnecessary sugars and calories.