Living, and by extension hiking and camping, in California provides a 9-month opportunity for rapid dehydration. Given the classic statistic of 'the average person needs to consume 2 litres of water on an average day', it prompts that a person exerting in hot, dry air will need to consume more than 2 litres per day. Whilst Alex Hutchinson points out in his book Endure that the body has a good tolerance of dehydration, and that on the other end of the scale there's a risk of hyponatremia, I like to play it safe and have enough water to stay comfortably hydrated.
As I see it, there are two approaches to this: carry enough water for the entire exercise, or, re-supply along the way.
Water is heavy, relatively speaking: 1kg/l of potable water. For a full day's hiking in dry terrain, I like to have 3l of water available. I'll probably split this between 2l hydration bladder, and a 1l softflask. I like to use soft flasks due to their low mass, and low volume when empty (low volume = less space taken in a bag = more flexible packing).
The simplest method of treating water is to boil it, but this is time-consuming, and renders the water far hotter than one may want. Other common methods include sterilisation tablets, or iodine, both of which can impart an odd flavour.
The TrailShot has the advantage of being small, weighing 140g, and can be operated one-handed, allowing one to drink directly from the source if required. It meets U.S. EPA drinking water standards and NSF protocol P231 for removal of bacteria (99.9999%), protozoa (99.9%), and particulates, and more importantly after being used in both standing and running water has prevented dehydration with a feeling of safety. It's only downside is that it has no taste filter, so while the water should be clean, if the taste of 'lake' is not to one's palette, it is not going to be the best filter for one.
The Grayl, on the other hand, does have a taste filter. It weighs 309g, and cannot be operated one-handed. You also need a firm surface to press down on. It removes 99.9999% of viruses (e.g. Hepatitis A, SARS, Rotavirus); 99.9999% of disease-causing bacteria (e.g. E. coli, Salmonella); and 99.999% of protozoan cysts (e.g. Giardia), which is of interest when compared to the TrailShot which does not filter flavour or viral bodies. Whilst it's not as small, or light, or trivial to use as the TrailShot, it is still a very efficient system that provides more protection, and it's own method of storing water.
This always feels like a gamble, but some trails and campsites have water fountains at them (not all, and not all are described accuratel). Some maps include the location of potable water, such as those provided by Garmin, however one is trusting them with one's (de)hydration.
Sodium, electrolytes, et al
As Gatorade knows, it's about as simple as adding a bit of sugar and salt to water, and charging for it. Beyond that, it appears to be mostly magic, and marketing. That said, I find that something electrolyte-ish makes me feel better when exerting, so I'll either have Hammer Endurolytes or Probar Bolt Energy Chews. They Endurolytes have ginger in, which is nice, and the energy chews are very nice. There are arguments that anyone on the Standard American Diet doesn't need extra sodium, but that's best kept between one and one's nutritionist.