Reduce dairy (preferably cut out any mucous causing foods)
What I mentioned above are just band aids. Finding the root cause is better for long term health:
See a natural Dr
Most people just find it annoying but we must realize that this is a sign of what could be a serious health concern! People can die from side effect from sleep apnea. Insurance should help cover the testing & machine. If yours doesn't, I think the life of your loved one is worth the money you'll spend!
For your marriage sake & their health encourage your spouse to get help ASAP!