Dehydration is the lack of intake of water to the body. Common signs of dehydration are headaches, weakness, vomiting (Heatstroke-related) and feeling "out of it" after strenuous work such as running, climbing, etc. Dehydration is common as it gets hotter in the location/area you are in. The recommended intake of water at 90F is about a gallon for every two hours at rest and up to three or four if active or in the sun. Non alcoholic fluids are better since alcohol dries you out (a hangover is dehydration) Soda isnt that good either, however, water and Gatorade-like fluids are the best to consume when dehydration is a threat.
__________________________________________________________________ Get a "Camel-Back" style hydration pack and it can serve 2 purposes: * It holds a liter of water to keep you hydrated AND * It can serve as a credibility prop: "Yes I am just hiking here, see my cool-looking hydration pack" at the same time, it hides all of your useful UE gear inside.