You can calculate the amount of sugar added (rule of thumb, 1 teaspoon of sugar/honey/syrup/rock sugar is 5g) and divide it by the total amount of ingredients in the drink/dessert, followed by multiplying the answer by 100. Your final answer should be ≤5g sugar/100ml. Otherwise, you must further reduce the amount of sugar added so that the end product will contain only ≤5g sugar/100ml.

E.g.: 2 teaspoons (10g) of sugar are added when making 500ml barley water. Hence, the calculation of the amount of sugar in the drink is shown as below.10/500 x 100 = 2g sugar / 100ml