During the summertime, it's key that you stay hydrated, especially when temperatures top 75 degrees. However, as refreshing as a glass of cold water is, sometimes we need variation in our beverage choices. There are plenty of healthy drinks lining the shelves of supermarkets, too, such as low sugar-bottled smoothies like Koia Smoothies and even fiber-rich soda alternatives like OLIPOP. We called on several health experts to share what their top picks are. Here are eight healthy drinks registered dietitians day you should sip…