I'm most of the way through my 2nd 26 serving bottle of Hammer Gel from Hammer Nutrition. The first flavor I got was Tropical and the 2nd was Espresso. Of the 10 flavors available, these are the 2 flavors that contain caffeine and that is what I was looking for. Now the tropical has 25mg of Caffeine and the Espresso has 50mg. To put that in perspective, a 12 oz can of Mt Dew has 55mg of Caffeine and a 12oz can of Diet Coke has 45mg (12oz of Starbucks coffee has around 250mg). So a 1 oz serving of Espresso does have about the same 'kick' as a can of soda, and at 90 Calories it packs a good amount of energy. Luckily it is a much slower burn than the sugar rush you get from soda.
As far as taste goes, the tropical had a very light sweet flavor and went down very easy especially in the heat of the summer. The espresso, is a lot heavier, it kind of tastes like pure chocolate syrup. So be ready for that. It's pretty strong and a little harder on the stomach in my opinion.
During a long run I will usually have a single serving mixed up to take before my run. I'll mix 2 or 3 servings to take with me. About 5 miles into the run I'll drink 1/2 of my nutrition bottle, then at around 9-10 miles (depending on total distance) I'll drink the rest. This provides a nice steady stream of energy for me.
The 26 serving size is great. I use the 5oz nutrition bottle that came with my Nathan hydration belt and can take as much or as little as I need without having all the foil packs. And at $0.77 a serving it's about 1/2 the cost of single serving foil packs. That is certainly what initially drew me to Hammer Gel over other Gels. I also emailed the company and confirmed that I can mix up some with water and don't have to refrigerate it overnight. So I can get my stuff ready the night before a 4:45am long run.
I've tried single packs of Vanilla and Montana Huckleberry. They were very good, the Vanilla totally tasted like frosting. One thing I do wish is that Hammer would put out a lighter flavor with the higher caffeine content of the Espresso.
One thing I keep reading is to use practice race day nutrition and hydration. So I will certainly be taking Hammer Gel with me when I run in St Louis in 50 days.