Place the pineapple tidbits and their juices with 3 cups of water in a blender; blend until smooth. If you want, before blending, reserve a couple of the pineapple chunks to use as garnish.
Pour the mixture into a saucepan using a strainer. Add the cinnamon stick and turn up the heat to medium-high.
Combine the masa-harina with the remaining 1 cup of the water. Mix well.
Once the pineapple mixture starts boiling, slowly stir in the masa-harina/water mix, using a strainer to avoid any lumps.
Add the sugar and keep cooking for 6-8 more minutes until mixture has thickened. Remove the cinnamon stick before serving; serve hot.