To take a random example off the web site - the list of ingredients of Lucozade Sport Hydro Active Drink are:
Water, Glucose Syrup, Citric Acid, Acidity Users (Sodium Citrate, Calcium Hydroxide, Calcium Carbonate), Flavouring, Preservative (Potassium Sorbate), Sweeteners (Aspartame, Acesulfame K), Vitamins (Niacin, E, Pantothenic Acid, B6, B12).
The only meaningful ingredients are water and glucose (vitamins do nothing in the very short term and anyone with a reasonably varied diet will already get enough). Glucose is a sugar. There are 10 calories per 100ml, which means it's very weak sugar-water If I want to drink weak sugar-water I'll drink diluted OJ or very dilute cordial.
Even taking pure glucose isn't really going to help me over taking the sucrose in more natural drinks - "In mammals, sucrose is very readily
digested in the
stomach into its component sugars, by acidic
hydrolysis." says wikipedia, and the component sugars are glucose and fructose.
Here are some more:
Lucozade sport "isotonic drink" has also got malto-dextrin, a slightly more complex carbohydrate. Lucozade sport "carbo-gel" is 89% glucose syrup - it's strong sugar-water. Lucozade sport recovery drink mix is sugar and "whey protein isolate (from milk") - it's sugary fat-free milk.
You can get all the alleged benefit of these things without all the gunk and marketing, and much cheaper, from proper food.