To treat dry mouth that occurs in the morning, treat the underlying cause of dry mouth. Most morning dry mouth is caused by blocked sinuses or snoring, so you need to treat those conditions to prevent dry mouth in the mornings.
A dry, sticky mouth upon waking is a sign that the person has breathed through his mouth during the night instead of breathing through his nose. This causes the breath to dry out the saliva on the tongue and teeth, causing a dry mouth. This can also lead to bad breath and a sore throat.
If blocked sinuses due to a cold or allergies are the cause of dry mouth, the sufferer may find relief from over-the-counter remedies for these illnesses. By clearing the sinuses, normal nose-breathing resumes, resulting in no more dry mouth.
If snoring or sleep apnea is the culprit, the treatment is trickier. Losing weight can help reduce the likelihood of snoring, but obstructive sleep apnea may require the use of a CPAP or continuous positive airway pressure machine. Ironically, this machine can also cause dry mouth if the person using it is a "mouth breather." To prevent dry mouth from the CPAP machine, a humidifier with a warm mist must be used with the machine.