You may have just started using CPAP or been using it for a while, then you notice waking up with a mouth full of dry crackers. Your throat is dry and uncomfortable. Here, Dr. Bhar - pulmonary and sleep doctor, will present a few reasons why:
Most devices come with predetermined settings, which may not be right for you. You may increase or decrease the humidity level (amount of water vapor). Give it 1-2 days to determine if the new setting helps. Check out these videos to adjust the humidifier on Respironics Dreamstation and ResMed Airsense.
You should be refilling the water tank every day or every other day. If this is not the case, your humidifier settings may be set too low or somehow not connecting to the machine.