The issue with oxygen saturation and sleep apnea is essentially that the drops cause damage, very slowly, over time. This is caused by physical restriction of the airway. When you're awake, your oxygen saturation is perfectly healthy (unless you have some other issue); increasing it for some period of time during waking hours wouldn't change the fact that it is dropping at night. CPAP treatment is the most effective way to treat sleep apnea, and your calibration test should confirm that your oxygen saturation is not dropping when you're on it. There are actually some studies on ways to increase the strength of the airway through various exercises (people who play reed instruments are much less likely to have sleep apnea, for example) but as far as I am aware none of them have become a recommended treatment, and in any case it would have to be measured with further sleep studies under the supervision of a doctor.