Begin by making the simple syrup (paggawa ng simple syrup). In a saucepan (kaserola), combine sugar (asukal) with 1 cup of water (tubig). Heat over medium heat (katamtamang init), stirring constantly until the sugar dissolves completely. Remove from heat and let it cool entirely to room temperature.

While the syrup cools, prepare the calamansi fruits. Wash them thoroughly (hugasan mabuti ang mga kalamansi), then roll each fruit on the counter using gentle pressure to help release more juice. Cut each calamansi in half crosswise.

Extract the juice using a citrus juicer or hand press (paniga ng kalamansi). If pressing by hand, avoid squeezing too hard to prevent bitter flavors from the pith. Strain the juice through a fine-mesh strainer (salaan) to remove seeds and pulp.

Once the simple syrup has cooled completely, combine it with the strained calamansi juice in a pitcher (pitsel). Add the remaining 3 cups of water and stir well to combine (haluing mabuti). Taste and adjust sweetness if needed by adding more simple syrup or water.

For best results, chill the juice thoroughly before serving. Serve in tall glasses over ice, optionally garnished with fresh calamansi slices or mint leaves. The juice should be consumed within 24 hours for optimal taste and vitamin content, though it can be stored in the refrigerator for up to 7 days.

For warm calamansi juice (traditional morning drink), simply mix the juice and syrup with hot water instead of cold.