Given the quantity of sports drinks on the UK market you could be forgiven for thinking that they were essential for anyone working out.
However the reality is that if you are exercising for less than 90 minutes, then the only sports drink you need is water. Only workouts longer than this will deplete the body's energy stores sufficiently to require the consumption of carbohydrates.
If you are interested in sports drinks, there are a few types to look for:
These are the most common, and the most useful. They have a fluid concentration similar to that of the blood, and are quickly absorbed into the blood stream. They thus perform two functions, helping to prevent dehydration, and also providing energy in the form of simple sugars.
These have a concentration that is lower than the blood and so are rapidly absorbed into the blood stream, but there are few hypotonic sports drinks on the UK market - except for water!
Hypertonic beverages have a higher concentration of carbs than blood, and thus need water from the blood to dilute them in the stomach - they can thus cause dehydration.
Hypertonic drinks have a carbohydrate content of greater than 8%, and are often no more than soft drinks marketed at the sports market. They are best avoided.
The conclusion is that that for most people, water is the drink of choice for working out. Be sure to drink plenty before, during, and after your workouts, and ignore the marketing of the sports drink companies.