I use water only. I take a couple thermotabs about 30 minutes before for electorlytes and then drink some powerade option after. I carry whole wheat peanut butter crackers for the simple and complex carbs and protien combination.
Ive read its best to drink a lot of fluids about 30-60 min. before or all day the day before a race and to not drink lots when riding or racing.
I tried mixing stuff in my bag but I dont clean it every time and some of the stuff that grows from leaving sugary stuff in there almost growls at me so I just skip the mixture all together and throw the bladder in the fridge after or the freezer for a couple hours before.