I do mostly unsupported rides of 100 or more miles. I ride a touring bike with three bottle racks.
bottle 1 - water
bottle 2 - 6 scoops maltodextrin & 2/3 scoop soy protein (lasts me three hours) This gives me about 280 kcal / hr. I used to do 4 hour bottles but that was like drinking pancake batter
bottle 3 - water