This syrup has multiple uses. Try it on ice cream or mixed with seltzer.
Combine raspberries, sugar, and water in a medium saucepan over medium-high heat. Cook, stirring occasionally, until raspberries break down slightly and release some of their juice, about 6 minutes. Remove from heat; let stand for 15 minutes. Strain mixture through a fine sieve, pressing down on solids to extract as much liquid as possible. Refrigerate for at least 1 hour.