Try eating a kiwi before you go out. And I take small sips of Heed. That stuff works miracles for me. I often mix in some BCAAs and Xtend. Studies are now showing that even swishing your mouth with a sports drink does enough (of course, not for super long runs - you WILL need fuel). I can't stand the Gu. I will use Shot Blocks and like those, plus the chewing motion is good because I will find that I set my jaw otherwise. Something like a Payday bar - about an inch or so bite here and there - can really give you a boost. And don't roll your eyes until you try it! A nice mix of carbs, some protein, a little fat. Pretty clean ingredient list too. If you are cramping like that, it sounds more like a deficiency and for 8 miles, you should be able to easily take care of that with something like the kiwi beforehand (load of potassium) and something like Heed or Endurolytes if it is very hot where you are.