I drink as much water as my belly will hold before I ride, really I force it in, then if I am riding more than 2-3 hours, I can drink more water.
On a all day ride, I will drink a sports drink at lunch, and mid afternoon, but only the sugarfree kind and cut at least half water. Another good drink to bring is V8, one can followed by water can really perk me up.
I snack on some kind of nuts for the salt & energy.
I prefer the cool-max type fabric because it is beastly humid here and that is the best for wicking in high humidity. All cotton shirts feel like I have put on a coat...HOT & HEAVY.
For the horses, they get electrolytes (plain no flavor kind) sprinkled over their food daily in the summer, I cut back if I see salt on their back, increase it a day or two before and after a long ride.
Plus I hose the horses after every ride, and add in a scoop of blue analgesic gel (dollar tree $1) in the water to help cool them down fast if they worked hard. That stuff cuts thru dirt and sweat really well.