Short story, a backpack.
In the summer, I drink a LOT of water. I carry 2x32 bottles in my frame and one or two in my backpack along with food that is still edible after sitting in a hot pack for a few hours. A backpack is not for everyone but dropping off prior or having a SAG is not an option for me in the rural routes either. My pack is a hydration type but I find it easier to just carry bottles in it instead of using the actual bladder and hose. I swap out frame bottles as they empty. The thought of having to wear something on my back for the main purpose of only carrying 32oz of additional water makes no sense to me and not worth it. Wearing a pack on a humid 95 degree day in the sun is also not ideal but so is running out of food and water. I've done solo isolated centuries with one and got used to it. You can even get hiking based fanny packs that can hold two bottles and have room for tools and some food (not enough for a long ride though). You won't win any style points and violate like 5 roadie rules with that option but consider those "rules" are not based on an unsupported rural century and not like there is an approved lycra wearing based plan for that.
Last edited by u235; 07-14-19 at 09:11 AM.