Hi...tongue and throat dryness during sleep can be due to many causes...
Do you have nasal blockage??( Can cause mouth breathing which causes dry throat)
Snoring??
Distorted sleep patterns?
Antihistamine use??
And chronic pharyngitis and GERD are some common causes
Next Steps
online consultation for detailed history and management
Health Tips
drink warm water...if your a professional voice user take care that you don't speak continuously for long periods...take break in between and drink water!!