A vote for a good hydro-pack.  I've not done the race but rather some longish sections - 1300-1800 miles in the last three years and used an Osprey hydro pack.  Very comfortable and I think I drink more water than if I had just plastic water bottles.  It has huge capacity for clothes, snacks and other items so it gives you flexibility.  It has small compartments on each side and in the hip belt which keeps me organized.