Put the demerara sugar and water in a small saucepan set over medium heat. Bring the mixture to a simmer, stirring often, until the sugar is dissolved, 2 to 3 minutes, and the mixture has thickened ever so slightly.
Remove the syrup from the heat and let cool completely.
Store the remaining syrup in a sealed glass jar in the fridge for up to 1 month.
Rum Breeze
Add all the ingredients to a shaker with ice and shake until well chilled. The shaker should be cold to the touch.
Strain into a stubby glass filled with crushed ice.
Garnish with a skewered brandied cherry or a pineapple wedge.