In a small saucepan combine the water, apple slices, and blueberries. Bring to boiling; reduce heat. Cover and simmer for 15 to 20 minutes or until apples are very tender. Cool mixture.
Puree mixture using a food mill, baby food grinder, blender, or food processor. Use within 1 day, or freeze for up to 1 month.
Spoon finished food into ice cube trays. Cover with waxed paper and freeze until firm. When ice cubes are frozen, remove cubes from tray and store in a resealable plastic freezer bag or freezer container. Label package with contents and date. Use within 1 month. Before serving, let thaw in the refrigerator overnight.