I also carry Endurolytes in my PSK, and keep Gatoraid in my office stash. I also keep water in an unopened commercial gallon-size container at the office. Because I wanted to keep it for a long time without having to replace for freshness, I decided on distilled - to keep bacteria from building up. Since distilled has no mineral content, it is especially important to keep Gatoraid of some other replacement handy if this is the way you want to go.