Yes, I am speaking of a intra- or peri-workout shake that is consumed throughout the course of the workout and diluted to a very low concentration (dissolved powder should take up only ~6%, iirc). It typically consists of easily absorped substances that take minimal to no digestion, i.e. amino acids, dextrose and it's polymers, electrolytes, etc.
Yes, gatorade is definitely sub-optimal, not only because of the fructose content in it's HFCS, but also because of it's brominated vegetable oil.
As for the study, I don't honestly remember where I read that. I will certainly look around and post what I find, but I'm just not sure if it was PubMed or something I came across at school or what. You can look for yourself too, if I don't come up with anything, just googling it ought to turn up some results.