Not fizzy, tart, or terribly sweet, coconut water is a unique mixer. "It is subtle, nutty, and hydrating. Mixed with spirits, it has a pleasant way of disappearing into the mix, stretching and smoothing out the flavor without stepping all over it." According to the article, it pairs especially well with rum and genever, but it even blends well with scotch!
Although canned coconut water will work — they ran their taste tests with Zico brand — juice from a fresh young coconut would be even nicer, especially if you drink the cocktail with a straw straight out of the hacked-open coconut. No paper umbrella necessary.
• Check it out: How to Drink Tropically at Esquire
Have you ever used coconut water as a mixer?