Magnesium is an essential mineral found in various beverages, including mineral water, soy milk, coconut milk, prune juice, green smoothies, and hot cocoa. Studies show that magnesium levels in mineral water can reach over 150 milligrams per liter, or 37.5 milligrams per cup. Studies show that magnesium levels in mineral water can reach over 150 milligrams per liter, or 37.5 milligrams per cup. How to enjoy it: Enjoy plain coconut water as a refreshing beverage or use it as a base for drinks like smoothies and mocktails. Like coconut water, coconut milk is a good source of magnesium, providing just under a quarter of your daily needs per cup.