why does water taste sweet when had after a gooseberry

Amla (Indian gooseberry) is a natural rich source of vitamin C which gets oxidised easily. The fruit contains 28 % of tannin which prevents this oxidation. When hydrolysed, tannin gives Gallic acid, Ellagic acid and Glucose which is sweet. As the disslution of glucose is an endothermic reaction a cooling effect is produced.