1. Mix sugar and cinnamon in a bowl. Add 1/2 teaspoon water. Stir to combine - you are looking for slightly moistened sugar. If sugar does not clump in your fingertips, add more water by the 1/4 teaspoon.
2. Fill the silicone molds to the brim and press to compact.
3. Rest overnight for the sugar cubes to dry and harden.
4. Lay a silicone mat or kitchen towel on a flat surface. Lay molds upside down and gently press each sugar cube out. Store in an airtight container for 1 month.