Bring the water to a boil in a large saucepan. Add the sugar and stir with a whisk (or use an immersion blender) until dissolved, about 1 minute (the water should become clear such that you can see the bottom of the pot). Stir in the molasses. Immediately remove from heat and let cool. Pour into a lidded bottle or other sealable container and store in the refrigerator. The syrup will keep, refrigerated, for several weeks.
NOTE: For a richer molasses flavor, increase the molasses-to-sugar ratio.