Remember from high school biology class, osmosis is the movement of water from a region of low salt concentration to high salt concentration. If you eat salt, then water follows that salt. Thus, it follows that a steady diet of salty foods increases the blood volume, requiring that the heart work harder . So the kidney works harder to flush out the salt, the heart works harder to deliver oxygen to the muscles, and YOU work harder because you have to transport and purify all the water necessary to keep your body reasonably balanced. That's what you are doing when you eat excess salt.
Most salt is lost through urine and perspiration.
Thus, even if you increased your perspiration volume and urinary output tenfold on the trail, you would still be getting enough sodium, given the typical American diet. I really sweat a lot. Not if you are eating over the course of the day. A salt tablet contains 500 mg sodium, so a handful of trail mix or a helping of instant soup provides the equivalent of one or two salt tablets. Caffeine is a diuretic, so you lose almost as much fluid as you gain by drinking the beverage.