What’s the most hydrating drink you can consume? And no, it’s not water. A study compared 13 of the most common drinks to find out which one keeps you hydrated the longest, and the results might surprise some people. Milk, both full-fat and skimmed, was the clear winner. But why? It’s because milk is rich in electrolytes like sodium and potassium, which help your body retain fluids longer. Plus, the proteins and fats in milk slow down the rate at which it leaves your stomach, meaning it stays in