My guess is one of two places:Great!
But where is Apple getting the 2 million masks?
1. They have a TON of construction going on, which are probably on hold due to COVID - they wear masks which the CDC has cleared are good enough for medical use for this pandemic, so that may be one source.
2. They have doctors and medical staff hired even for overseeing testing to that the "test subjects" go through for the AppleWatch and health apps, they wear them for sure, so they that could be another source.
But these are just my personal guesses.