I want to do an approx. 200k ride in a day, mostly flat, recreational. I don't have much training for this kind of distance but I have done it several times before and I know I can do it. However, every time I finish very "depleted" (bonking?), no cramps, but very few watts left. What should I eat during the ride to keep my reserves up, or is this this inevitable due to lack of training for the distance?