Fill the blender with the chopped cabbage.
Add 2 cups of water and salt.
Blend until smooth, adding more water if needed.
Pour blended mixture in a glass mason jar leaving about 2 inches of headroom.
Cover the jar securely with an airlock.
Let mixture stand at room temperature for 3-6 days (around 72º F) and out of direct sunlight.
When done, seal the jar with a plastic lid and transfer the fermented cabbage juice to the refrigerator.