Throughout my running career I have tested a few different products to try and find the perfect mid-run fueling option. A mid-run fuel is great for difficult half marathons, full marathons, and multi-day relay races like RAGNARs.
I will tell you upfront that all of these reviews are based off of my personal opinions and experiences. Plus, I have a very sensitive stomach while running, so that played a large part in my choices as well.
GU

I cannot use GU on my runs, I have thrown it back up every time. Here’s why I think I struggle…The consistency of GU is REALLY thick and goopy which sticks to all crevices of your mouth the moment it enters it, making it nearly impossible to swallow. Add to that the fact that a runner who needs GU is probably already at the state that their mouth and spit is dry and sticky to begin with…so there just isn’t an easy way to swallow this stuff.
Secondly, the flavors are very intense. I will admit I have a touchy stomach, especially when I’m running, so these strong flavors get rejected pretty quickly.
I have attempted the tri-berry, vanilla bean, and strawberry banana.
Gatorade Chews

First I’ll tell you why these chews only get 3 stars…and yes, I’m being picky. I have sensitive teeth and these are really sticky…so they stick to my teeth and make them hurt. HOWEVER, I do like to suck on them and get the glucose benefits from them that way.
I’ve tried the fruit punch and strawberry flavors. I prefer strawberry, but both are good.
Huma Gel

I love the texture of these gels, way less sticky, easier to swallow, etc. Plus they have the little chia seeds in them that kind of break up the gooey feeling and give you just a slight little crunch. Once again, I’m just being picky…but my stomach can’t handle these very well. I think I would have more luck using these for pre-workout quick glucose.
I tried the strawberry flavor, which is their best seller.
Honey Stinger Energy Gel

This is a personal preference for sure…and if you are not a fan of honey, you won’t like these. The gel packs are literally flavored honey with added electrolytes like sodium and potassium. These are the only gels I have found that a) don’t bug my stomach, b) have a good texture, and c) taste great!
I’ve tried the fruit smoothie flavors and the acai pomegranate…both are great.
Nuun

Nuun are circular tabs you can add to your water to give it flavor and add electrolytes (and in some cases vitamins). I have written blog posts in the past that talk about how much I love Nuun…it really helps calm my stomach because of the slight carbonation. I have also recently fallen in love with nibbling on the tabs themselves and having them fizz in my mouth.
Nuun however is not an energy source, there are very few calories in this drink. The drink is more about getting a source of electrolytes during runs to keep you from getting dehydrated.
My favorite flavors are watermelon, strawberry lemonade, and citrus.
All statements in this post are my personal opinion, I was not compensated by any of these companies to try or review their products, these are just the honest OPINIONS of a runner.