Coconut water is not water with coconut flavor added. It's the clear fluid inside the coconut, not to be confused with coconut milk, which is an emulsion of coconut water and fresh grated coconut. So coconut water is a type of juice.
Unlike other juices, unflavored coconut water is low in sugar and calories. Ounce for ounce, typical fruit juices have twice as many calories as unflavored coconut water.
Coconut water is popularly used for rehydration after physical activity or an illness such as diarrhea. It's true that coconut water has natural electrolytes — such as potassium, sodium and manganese — but amounts can vary due to changes that occur in coconut water as the coconut matures.
So, while there's some evidence suggesting coconut water may be comparable to having a sports drink, there's also evidence that coconut water may be no more effective than drinking plain water.
The potassium contained in coconut water can be a benefit to you. Americans typically don't get enough potassium. However, coconut water also contains sodium. That might be a concern if you, like most Americans, already have too much sodium in your diet.
As a casual beverage, coconut water is considered safe. Coconut water does have calories — 45 to 60 calories in an 8-ounce serving. Weighing the pros and cons, plain water is still the smart choice.