Put cranberries, water, and sugar in a medium saucepan and bring to a boil.
Lower the heat to a simmer and continue to cook for about 10 minutes, until the berries are just starting to burst.
Remove the saucepan from the heat and pour mixture through a fine mesh strainer placed over a bowl. Press with the back of a wooden spoon to extract as much liquid from the cranberries as possible.
Keep syrup in bowl or pour into jar and place in fridge to cool completely before using.