2¼ cups (560 ml / 19 oz) water, warm or room temperature
2¾ cups (625 g / 1.38 lb) white granulated sugar
1 oz (28 g) orange syrup concentrate
Cold seltzer water
Pour the water into a 2-quart or larger pan.
Add the sugar to the water. Stir until the sugar dissolves.
Add the concentrate to the sugar water. Stir until mixed.
Using a funnel, add the syrup to an empty plastic bottle (make sure to close it with its cap when done). Refrigerate until cold.
Fill any glass halfway with seltzer water. From the bottle, add the syrup to the glass. Stir until mixed (optional).