As we know, water is essential for life more than food, and will always be something that we have to take any outdoor activity of some physical intensity or duration. Water is not only necessary for drinking, but can also be useful (for example) to clean a wound by applying first aid. Therefore always be taken into account, and know for sure where in the road is water (whether natural or artificial sources), and in any case bring water reserve in case, if only to have along the route to any incident.
The food is less necessary, especially during take less than a day (especially if we ate well before you leave). But it all depends, of course, our level of training and practice, because maybe there can be a person who has no problem with not eating for 5 hours, others at the slightest physical effort they whet the appetite.
In any case, as happens with water, will always bring some food to spare staff on carbohydrates (glucose or sugar), or an energy bar, dried fruit or something. If someone suffers a relapse of physical exhaustion, eating sugar the “revival” for at least 20 minutes, maybe you need to keep moving on their own to reach their destination, where you can rest and eat better.
On the consumption of water or isotonic drinks before and during the activity, if we have no personal experience in the field, we can begin to be guided by the recommendations mentioned here . With regard to food intake, particularly carbohydrate before and during activity, we also consider these recommendations to avoid problems of physical relapse during our journey.