I'm not sure why anyone would want to make their own drink? Cost? Knowledge of the ingredients? Companies like SIS, Powerbar, Lucozade etc spend millions in R and D on these drinks. I'm sure that you could make a drink (of sorts) but its not going to be as honed as, lets say SIS PSP22 is it?? and would you use it in a race, I wouldnt!! Anything from olympic, 70.3 or full ironman distance races and your gonna need pukka fueling to keep going, a bottle of Ribena with some salt and sugar aint gonna cut it.