I spoke to the Special Needs department last week about something else* and they confirmed distilled water would be provided for my husband's CPAP and that we should probably bring our own extension cord. However, he will be carrying a small supply of water just in case (you can get it in 12, 16, or 20oz bottles marked "for medical use" on Amazon, etc. so it's easy to put in a checked bag for airtravel)
*I wouldn't have needed to call them but my e-docs said I needed wheelchair assistance. I do not. They (and I) were confused about how that happened. On the other hand, if you're on the BA next week and DO need a chair, we've got one freed up for you! 🙂