Best move I made was getting a hydration pack. When I head out, I fill the pack with water and then fill my water bottle with Gatorade. Water keeps me hydrated and the Gatorade helps replace the electrolytes I lose through sweat.

If you frequently travel with a standard backpack (I use one when I commute to work), instead of a full hydration pack, you can get a "bladder" that you can stow in, or attach to, your backpack. The one I got holds 3 litres of water. Got mine from Mountain Equipment Co-op (great store here in Canada). Go to www.mec.ca and search for Hydration. Bladders are a cheap and portable (I throw mine in my fishing vest) solution to help with hydration.