Add sugar and soy milk to a medium pot over medium high heat. Stir until all the sugar has dissolved then bring the mixture to a low simmer.
Continue to cook the mixture down for roughly 55 minutes, or until the volume has reduced by half. You can always pour out the mixture into a measuring cup to gauge how much it has reduced if you're not sure. Do not increase the heat, cook the mixture low and slow, it will slowly start to thicken and become a little more viscous.
Once the volume has reduced by half, transfer it to a sterile mason jar or other airtight container and allow to cool to room temperature. The mixture will thicken as it cools. Once completely cool, cover and store in the refrigerator.