Start with what you tolerate
Use training to observe what you already drink comfortably, then note duration, conditions and how it felt.
Plan the logistics
Decide where bottles or aid stations will be and how many servings are realistically available.
Avoid last-minute changes
Race day is not the best place to first test a new drink or unusual amount.
Takeaway
Test changes in training, adjust gradually and do not turn general information into personal diagnosis.