Add the pineapple, water, and sugar into a large blender. Blend for 1 to 2 minutes until smooth. You may have to do this in batches if your blender isn't big enough.
Taste and blend in more sugar if desired. Strain the mixture into a pitcher to remove any pulp.
Serve immediately over ice or chill in the refrigerator for up to 3 days.
Notes
You can adjust the amount of sugar based on the ripeness of your cantaloupe or to your liking. For a less sweet agua fresca, only use half of the sugar.
If you like pulp, you can omit straining the mixture.
Add a squeeze of lemon or lime for a fresh citrus twist!