Many times a patient with sleep apnea will keep their mouth open unconsciously at night to breathe better. This can cause a dry mouth sore throat the next morning.
Pressure sensors placed inside sleep apnea patients reveal that every time an apnea occurs, a tremendous vacuum effect is created inside the chest and throat, which literally suctions up your normal stomach juices into your esophagus and throat.
To help avoid a sore throat, do not eat or drink close to bed time. If you happen to have a late meal or a snack just before bedtime, there will be even more stomach juices lingering in your stomach to come up into the throat. If you have sleep apnea, this would just add to your already existing issues.