Start early
Hunger is a late signal during endurance exercise. By the time you feel depleted, catching up can be difficult.
A practical plan begins early and repeats at a rhythm your stomach can tolerate. The exact amount depends on the athlete, the duration, the intensity, and what has been practiced.
Train your gut
Use training runs to test timing, products, fluids, and quantities. Change one variable at a time. Write down what happened. Race day should feel familiar, not experimental.
The best plan is not the most complicated one. It is the one you can follow when the miles get hard.