Could the plant have been hit by a cold draft? Perhaps it’s near a window? Sudden leaf-drop can be caused by cold damage. If that’s not the case, the best you can do is keep it in a warm, partly-sunny place and let the soil dry out as usual. Let the top inch or two of soil dry out before watering again. Without its leaves, the plant can’t get rid of excess water as easily, so be careful not to overwater. Avoid fertilizing until leaves appear again. If the trunk and roots aren’t rotted, then the plant should recover.
Could the plant have been hit by a cold draft? Perhaps it’s near a window? Sudden leaf-drop can be caused by cold damage. If that’s not the case, the best you can do is keep it in a warm, partly-sunny place and let the soil dry out as usual. Let the top inch or two of soil dry out before watering again. Without its leaves, the plant can’t get rid of excess water as easily, so be careful not to overwater. Avoid fertilizing until leaves appear again. If the trunk and roots aren’t rotted, then the plant should recover.