Hi Funkybabe76,
My advice would be to steer clear of any foodstuff specifically targeted or labelled 'Diabetic', it invariably is a total waste of money.
You don't say if your parents are type 1 or 2, I ask this because most of these drinks are high carb/high sugar, which if they are type 2 would be totally unsuitable. If they are type 1, then these drinks are only good for quick sugar release to avert a 'Hypo' (sipped in moderation), and shouldn't really be used for any other purpose. Carbohydrate is what gives the body energy (Fuel, if you like), the problem with Diabetes is that the pancreas isn't producing insulin, or enough of it, to regulate the amount of Glucose in the bloodstream, therefore, Glucose drinks are best avoided.
Hope this helps.