Popular brands of sport drinks include Gatorade, Accelerade, and Powerade. These pre-made, often neon-colored drinks contain carbs that you need for quick energy, and sodium and water that you need for hydration. A proper sport drink contains about 15 grams of carbs and 110 mg of sodium per eight-ounce serving. You can also buy powders you mix with water to make sport drinks. You only really need these drinks if you are working out for an hour or longer or are sweating profusely during your workout. I wouldn't sip these while running on the treadmill for 30 minutes. The sugar isn't necessary for short workouts, and as long as you hydrate with water before and after exercising, you're good to go.
What about Smartwater? To find out
There are also beverages that contain electrolytes and no sugars, such as Smartwater or Function Water. Or if you want a little flavor but not a ton of sugar, NUUN tablets can be dissolved in your water. Electrolyte-enhanced water will help prevent dehydration but help your energy levels by providing glucose (aka sugar, which is turned into fuel for your muscles).
So here's the bottom line. If your workout is under an hour, drink plain water before and after. If you're working out and sweating a lot, sip electrolyte-enhanced water every 10 to 15 minutes while working out. If you're working out for an extended period of time, and are also sweating out fluids, sip a sports drink every 10 to 15 minutes.