I've been using Infinit. It's a custom energy/electrolyte powder that you mix with water. It sounds complicated but it's not. The website has a system of sliders and questions that help you make up the correct drink for you.

You can decide the amount of calories, type of carbs, amount of electrolytes, whether you want protein or not, and even the strength of the flavor. I love the flavor feature because I hate really sweet drinks after a few hours on a ride.

It costs about the same as the Hammer products.