Wash to remove any dirt from the star fruit and ginger, then chop into smaller pieces.
Add the ginger and star fruit to a blender with water and blend until smooth. Depending on the size of your blender, you may have to blend more than one batch.
Strain using a sieve or a cheesecloth. Cheesecloth is best to keep things more tidy.
Add the lime juice and sweeten with sugar. Put to chill or serve over lots of ice.
Notes
When washing the star fruit, make sure the clean around the stem area.
Use both the juicy yellow start fruit and the greener ones. The yellow start fruits are sweeter, and the greener ones have a tangy-sour taste, which combines to give the drink a nice flavour.
I used brown sugar, but you can use granulated sugar.