Bag of Holding:
[...] Breathing creatures inside the bag can survive up to a number of minutes equal to 10 divided by the number of creatures (minimum 1 minute), after which time they begin to suffocate. (DMG pp. 153-154)
Cap of water breathing:
While wearing this cap underwater, you can speak its command word as an action to create a bubble of air around your head. It allows you to breathe normally underwater. This bubble stays with you until you speak the command word again, the cap is removed, or you are no longer underwater. (DMG p.157)
Cloak of the manta ray:
While wearing this cloak with its hood up, you can breathe underwater, and you have a swimming speed of 60 feet. Pulling the hood up or down requires an action. (DMG p.159)
Can a creature wear the cap or the cloak and hide inside the bag of holding for an unlimited amount of time (and not just 10 minutes)? I am pretty sure that the cap allows it, while the cloak description does not specify how the breathing process is performed