Within the UK Dioralyte is a product taken after a bout of diarrhea, it's a product such as this which is required; not sports rehydration drinks, as they may contain too much sugar, I guess other than glucose, which can have a negative effect.
I make my own solution by following the St Marks emix recipe:
20g (six level 5ml spoonfuls) of glucose
2.5g (one heaped 2.5ml spoonful) of sodium bicarbonate
3.5g (one level 5ml spoonful) of sodium chloride (salt)
Dissolved in 1 Litre of tap water.
The following is an extract from the St Marks emix solution pdf:
Drinking Two to Three litres per day may be necessary to maintain hydration.
The powders can be purchased from Pharmacies and Supermarkets, and will be cheaper than a NHS prescription charge.
The patient may find the solution bitter in taste due to the Sodium Bicarbonate; this can be minimised by storing the solution in the refrigerator and by the addition of a small amount of fruit juice or flavoured squash and sipping through a straw.
If this continues to be a problem, the Sodium Bicarbonate can be replaced by the same quantity of Sodium Citrate.