Depends on how soon you have to get underway. But, if you are like most alpine climbers, you do not have time to lounge around, and pre-dawn starts are the order of the day. "It's latter than you think is always true in the mountains"
Therefore, breakfast should be high in carbohydrates so that blood does not have to be diverted to the stomach for digestion and thus take away vital strength from the leg and arm muscles that are needed for climbing and hiking.
A) Instant oatmeal with protein powder, powdered milk, and sugar.(Can be eaten cold)
B) Pop Tarts (Very fast breakfast but short lasting energy source)
C) Granola with dried fruit (the fruit will help keep you regular)
D) Energy Bars (longer lasting energy, but harder to digest when you are active)
E) Plenty of Water (If you are thirsty, you are already dehydrated)
F) Hot Cocoa (If you have time. Cocoa can be a great starter, but be aware that more water will be needed since Cocoa contains caffeine which is a diuretic.)
Starts right after breakfast. During exercise things change. Performance dips, if blood has to be diverted to the stomach for digestion. Bill Vaughan, who helped formulate the original energy bars, then developed carbohydrate gels, which are easily ingested and efficiently utilized during exercise. He came up with a product called GU, a gel that supplies 25 grams of carbohydrate in the form of glucose polymers and fructose. The gel, when combined with a couple of mouthfuls of plain water achieves the solution of 4 percent to 8 percent carbohydrates ideal for gastric emptying. GU contains leucine and valine, two of the branched chain amino acids that are burned up during exercise but are essential for physical activity and muscle recovery. GU also contains a small amount of caffeine to aid fat metabolism to help keep your mind alert.
Experts suggest that you ingest 1-2 packs of GU or equivalent per hour. It provides all the energy you need while under load, and enters the blood stream in minutes. Mix with water as you go. The body cannot absorb more than 400 calories per hour during exercise without inhibiting gastric emptying, and GU works good for this. But not everyone will take this route, and most opt for other solutions. However, foods such as meats, energy bars, and other sources require blood to be diverted to the stomach, and performance will suffer. As always, make sure to get down plenty of water. Water, next to oxygen is the most vital substance that your body needs during a hike or climb.