Howdy Rick,
During endurance exercise lasting up to 24 hours, your primary needs are water, carbohydrate, and sodium. Dehydration can happen sooner than muscle glycogen depletion, so ultimately water is the key nutrient for both health and performance.
I like Gatorade and carry at least 2 liters in the winter and at least 3 liters in the summer for day hikes. In the summer, I use Gatorade Endurance due to the higher sodium content (I'm a salty sweater) and in the winter I use regular Gatorade.
I've worked with numerous endurance and ultra-endurance athletes (runner, cyclists, triathletes and hikers). Most of them have tried different sports drinks and found one that "works' for them. Some athletes drink water and carry carbohydrate and sodium sources (e.g. higher sodium sports gels, pretzels, etc.)
Research with ultra-endurance athletes indicates that we can "burn" up to 1 gram of carbohydrate per kg per hour. During warm hikes, I generally go through one pint or more of Gatorade an hour and one gel an hour. This gives me about 40 grams of carbohydrate, well within what I can burn. Liquid and solid carbohydrates are equally effective -- each has advantages and drawbacks.
The optimum carbohydrate concentration for a sports drink is 4 to 8%. More concentrated drinks are absorbed more slowly, as Bivouac pointed out. This not only slows the water getting into your blood, but can also cause gut distress. Soft drinks and fruit juices have 12 to 15% carbohydrate. Since you're drinking the same amount of water after the soda, you've effectively reduced the carbohydrate content to acceptable amounts.
Some ultra-endurance athletes (Ironman triathletes, Tour de France cyclists) use products that are 18-24% carbohydrate such as CarboPro and InfiniT. The rationale is that they can carry alot of calories in their feed bottle. However, they also carry a water bottle and obtain water and/or sports drinks at aid stations. They cosnume a certain portion of the bottle each hour and dilute it with water to meet their carbohydrate requirements.
Hypontremia (low blood sodium) is a concern during ultra-endurance exercise lasting over four hours. A continous decrease in blood sodium causes rapid entry of water into the brain. This causes brain swelling (cerebral edema) and a series of neurological responses (confusion, seizure, coma) that can end in death from brainstem rupture.
Hyponatremia is primarily caused by consuming an amount of fluid that exceeds sweat and urinary water losses. The most likely explanation for exercise-associated hyponatremia is that excessive drinking reduces the plasma sodium concentration.
In endurance events such as the marathon, symptomatic hyponatremia is more likely to occur in smaller individuals who run slowly, sweat less, and drink excessively before, during, and after the race.
During prolonged endurance exercise such as an Ironman triathlon, high sweat rates and a high sweat sodium concentration (“salty sweat”) can also contribute to hyponatremia. Large sweat sodium losses confer a greater risk of developing hyponatremia because less fluid intake is required to produce dangerously low blood sodium levels.
Now to bring this back to hiking...
Hyponatremia has occured in individuals hiking the Grand Canyon. To my knowledge, it isn't common in hiking otherwise. I think some people hiking the canyon over-drink on the way down when they aren't sweating much and so dilute their sodium level.
Regarding your situation....
You've probably been fine because your sweat rate has matched or exceded your fluid intake. Consuming salty snacks or higher sodium sports drinks helps to maintain blood sodium levels as well.
I encourage athletes in endurance events (including hikers) to measure their sweat rates during different environmental conditions. That is the only way to know how much to drink. If an athlete gains weight after a workout, he or she is over-drinking. If an athlete loses over 2% of body weight during a workout, he or she is getting dehydrated and needs to drink more.
OK -- it's 5 PM now and I'm off the clock
Hope this helps.
Miles of smiles,
Ellen