You could make the argument that the Apple Watch can be used to manage your sleep apnea condition. On the off chance you get audited by the IRS you might just be better off paying for it with non-HSA funds rather than dealing with that mess.
PSA: HSA expenses are based on the honor system, but obviously don't go to Best Buy and buy a PS5 on a HSA debit card. You are allowed to reimburse yourself for medical purchases. For example, if you have a large ticket medical expense you can use a credit card that provides a perk like air miles and then just transfer the funds from your HSA checking account to your regular checking account. Just remember to keep detailed records/receipts.
This is the same with an HSA. The difference is that you can invest funds from an HSA and the growth is tax free.
I could imagine a case where I'd start an FSA. An HSA did not work out well for me a few years ago when I tried it, and would be even less likely to be a win for me now.