Add the raspberries, sugar, and water to a small heavy bottomed saucepan and heat over medium-high heat until it comes to a boil. Reduce heat to medium-low and simmer, stirring occasionally, until the raspberries have begun to break down and the mixture has reduced slightly, about 10-15 minutes.
Strain through a fine mesh strainer into a bowl or large measuring cup, preferably with a pouring spout. Discard the raspberry solids and let the syrup cool to room temperature. Transfer to a bottle (or other airtight container) and store in the refrigerator for up to two weeks.
Alternatively you can include the raspberry solids, or blend them with the syrup to create a thicker consistency.