Ideally eat some hearty breakfast well before the hike start.

In summer time usually I bring 0.5-1 litre of liquids per hour of expected time walking/running. Mostly water but also Gatorade or similar energy drinks. Your sweating level would define how much you need, but it is always better to carry above your requirements than having too little under the scorching sun.

For over 3 hours of total hike or in paths where I expect to stop several times I bring some food: sandwich, fruit, nuts, bars…