Remove the leaves and stems of the bilimbi fruit & wash in 2-3 changes of water.
Drain and then pat them dryWithout using any water, grind the fruit to a fine paste. You can chop the fruit if required.
Strain the paste into a bowl. Squeeze the pulp to extract as much juice as possible. You can grind the pulp again to remove more juice but it is not necessary.
Add 2-3 drops of the green food colour (optional) and stir.
Weigh the juice in grams using a kitchen weighing scale. We need to take an equal amount of sugar (in grams). I got approximately 350 grams of juice and I used 350 grams of sugar which is 1-3/4th cups. Now in the ratio of 1:1, take an equal amount of water (in volume = cups), so I used 1-3/4th cups of water.
To make the syrup, place the sugar & water in a saucepan and bring the mixture to a boil. Stir to dissolve the sugar and then let the mixture thicken on a medium low heat till you get a one string consistency. This process can take around 12-15 minutes so have patience. To check the consistency, take a drop of the syrup and cool it for a few seconds. Dab the liquid between your thumb and index finger and press them together. When you release the two fingers, a delicate thread should form between the fingers. When this consistency has been achieved, remove the saucepan from the heat and allow it to cool completely.
When the syrup cools down to room temperature, add the juice to it and mix well.
Store the mixture in a clean, dry & sterile bottle.
To prepare the drink, dilute 2 tablespoons of the mixture in 200 ml of water, plain or chilled. Stir and serve! You can also use sparkling water or unflavoured soda to give this drink a special twist!