Since I get all my sleep apnea supplies from the VA, but I am not rated for sleep apnea, should I put in a disability claim for it?

Yes .. and no. If you're already at 100% P&T, then obviously your rating won't increase if you're given a rating for sleep apnea.

Aside from a person satisfaction that you're received a rating for something that was service connected, the only real effect is possibly allowing your family to receive DIC survivor benefits after you have shuffled off this mortal coil.

If you're 100% P&T or TDIU, then even if you died from a non-service connected cause your survivors will generally receive DIC (as long as the cause of death wasn't your own misconduct) if one of the following applies:
• You've had that rating continuously for at least 10 years before your death; or
• You've had that rating continuously for at least 5 years before your death and have had that rating since your release from active duty; or
• You've had that rating continuously for at least 1 year before your death and you were a former POW.

One thing to keep in mind - while the VA says that filing for a benefit won't affect your previous benefits most VSOs will tell you that if you are already rated at 100%, then don't file for a new service-connected condition, or if you are going to file, to wait until the VA's '5-year rule' kicks in (after you've held that rating for five years, the VA must show that your condition has significantly improved before they can lower the rating).

Yes

If you're at 100%, adding more claims will do nothing for your percentage, obviously. Since you receive your supplies from the VA, I'm assuming that you had a sleep study done since you've been out? Since they are providing you will the CPAP and supplies, I wouldn't poke the bear.

My Sleep apnea was diagnosed while I was on active duty, so it was part of my initial claim. Other groups that I'm in for VA related claims are pretty big on not trying to add anything once you've received the P&T status.