Combine 2 cups of the water and the sugar in a small saucepan. Heat over medium-low, stirring occasionally, until the sugar dissolves completely. Do not boil. Remove from the heat and cool to room temperature.
Pour the cooled syrup into a large pitcher with the remaining water.
Juice the oranges through a fine-mesh strainer directly into the pitcher.
Remove the seeds and large pieces of pith from the strainer, then stir the strained pulp into the pitcher.
Stir until well combined. Taste and add more water, if desired, for a milder flavor.
Pour over ice, garnish with orange slices if desired, and serve immediately.
Notes
Freshly squeezed orange juice provides the best flavor. Bottled orange juice is not recommended.
Chill the orangeade for at least 1 hour before serving for the freshest, most refreshing flavor.
Stir before serving, as the fresh orange pulp will naturally settle to the bottom of the pitcher.
Store covered in the refrigerator for up to 4 days.
For a honey-sweetened variation, substitute ½ cup of mild honey for the sugar and dissolve it in the warm water as directed.