For years I've heard hikers talk about carrying a protein suplement along on trips to ensure that they don't sacrifice muscle while hiking.
Most people who have ever tried a protein powdered drink mix don't keep that idea very long. The taste usually speaks for itself.
Enter Muscle Milk, Especially their Strawberry and Cookies n Cream flavors. Two scoops (75g) mixed with cold water makes an impossibly good milkshake that is satisfying, filling, and, believe it or not, full of energy. There's 32 g of protein, but also a healthy dose of fat, carbs, and plenty of vitamins mixed in.
It was as satisfying as an energy bar but with no "crash" 30 minutes later. The milkshake like quality was a pleasant treat, and it stayed with me for hours.
Surprisingly, I didn't care for the Chocolate or Vanilla flavors, however. They had a strange aftertaste.
I would question using an energy shake in a very hot enviornment, but for normal hiking this will have a permanant place on my menu.
Edit: I gave this a 4 mainly because of the weight. The taste was great!