Here is a list of things you will typically find at aid station in 50 to 100 mile races:
Water and energy drinks
Sandwiches, peanut butter and jelly, ham and cheese, etc (sometimes grilled)
M&Ms, Gummy Bears, and other types of candy (hard and soft)
Potato Chips and Pretzels
Some not-so-typical aid station foods found in 100 milers:
Fried or boiled eggs
Bacon and ham and eggs with pancakes (I would sit down to eat that)
Some aid stations have grills ready to prepare what you want.
At the Tahoe Rim Trail 100, Diamond Hill aid station is located at mile 30 and 70 and they kept grills going all day and all night. They were ready to make about any thing you wanted.
Most of these mixes have carbs and protein plus a lot of other supplements. I now use Carbo Pro which is 100% Complex Carbs. It has almost no taste at all and I can drink it for 27 straight hours with no problems. (Well, at least at Rocky Raccoon) I eat enough other stuff, like peanut butter and jelly sandwiches and other stuff at the aid stations to get the protein, I guess. There are many brands and types of energy drinks to choose form. Most are available in individual servings, so buy an assortment of brands and flavors and try them all. Try the carbs and protein combinations and try straight "complex" carbs, too. Experiment with different water/powder ratios. I carry 10oz water bottles on a Nathan Speed 4R belt during long runs and races and mix the Carbo Pro at a ration of two scoops of powder to 10 oz of water. At this ration one 10 oz bottle should last about one to one and a half hours. In races, I add powder to all four bottles but only add water to one bottle at a time, (unless it is going to take a long time to get to the next aid station.) As you approach the next aid station, pull out the next bottle containing powder and add water. That way, you are not starting the race with 2.5 lbs of premixed liquid.
(at the Run for Kids there is room for a cooler at the aid station.)