For anyone with sever deviated septum who has trouble sleeping because they can't breath through their nose which often causes excessive dry mouth, I highly recommend trying [1] Nose Vents.

Since using them I get much better sleep, don't wake up with dry mouth and a need to drink water all night. It only takes a few nights to get used to them. I use the largest silicone pair, despite the fact that it seems like its a tad to large, because it widens the nostril to ease breathing. Your mileage may vary.

[1] https://www.amazon.com/gp/product/B0743KZK88/