Rinse fresh blueberries under cool water and pat them completely dry. If using frozen blueberries, let them thaw for about 10 minutes at room temperature.

Combine blueberries, Greek yogurt, and water in a blender or food processor. Pulse until the mixture reaches your desired consistency - smooth or with small fruit chunks.

Pour the mixture into ice cube trays, silicone molds, or small paper cups. Leave about 1/4 inch of space at the top since the mixture will expand when frozen. Tap the molds gently to release air bubbles.

Insert popsicle sticks or small dog biscuits into each mold if desired (optional). Skip sticks if your dog tends to swallow things whole.

Place molds in the freezer for at least 4 hours or overnight until completely solid.