Chop rhubarb. Add to a pot with sugar and water and bring to a boil. Lower heat and let simmer for 15 min.
Strain through a sieve and transfer to the fridge to cool. To use, pour some syrup into a glass and top with sparkling water till it’s sweetened to taste. To store the syrup, strain into into a glass bottle and store in the fridge where it will keep for at least 2 weeks. Enjoy!