The mouthpiece attached to the hose should be able to be gently pushed back along the strap of the pack. The whole bag comes out. To wash it, I detach the mouthpiece and the hose from the bottom of the bag (you gotta pull hard). I use a baby bottle brush to wash out the bag. There a tablet sold which is dropped into the bag to clean it and keep it fresh but I don't use it. I hang the bag over the sink to dry. I place waded paper towels inside the bag to keep it open and dry faster. There is a plastic frame sold that does the same thing.
Ernest