The invention relates to a method for temporarily increasing the resistance to vertical compression of a bag for transporting and holding liquids and quasi-liquids, intended for a bag having the general shape of a cube and including receptacles of each of the corners thereof. The method consists in choosing four inflatable cushioning pouches for each bag, said pouches being elongate and having length, width and extension dimensions corresponding to the length, width and internal volume of the receptacles in the bag. Next, the four cushioning pouches are introduced into the four receptacles and are subsequently inflated, thereby trapping same in a vertical position in which they can resist compression along the vertical axis thereof. The resulting bag is characterized in that the receptacles in the four corners of the bag are each provided internally with a cushioning pouch which is optionally rigidly secured to the bag.
