Begin by cutting the pineapple into chunks. Discard the skin and core, keeping only the flesh. Aim for bite-sized pieces to facilitate blending.
Add the pineapple chunks from Step 1 to your blender. Pour in 4 cups of cold filtered water. Blend for about 2 minutes, or until the pineapple is completely broken down and you have a smooth liquid.
Taste the blended pineapple water. If you'd like it sweeter, add 1 to 2 tablespoons of your preferred sweetener. Blend briefly to mix. If your blender doesn't fully break down the fibers, strain the mixture through a fine mesh sieve to remove any remaining pulp. Personally, I always taste and sweeten gradually—it’s easy to add more, but impossible to take sweetness out!
Pour the finished pineapple water into a pitcher or bottle. Chill in the refrigerator for 30 minutes to 1 hour, or serve immediately over ice. Store any leftovers in a tightly sealed jar or bottle in the refrigerator for up to 3-4 days.