An insert assembly (fitment) includes a container mounting element, a spout element carried by the mounting element, at least one support element and a grasp element suspended by the support element(s) below the mounting element. The grasp element provides a skeleton within a pouch-type flexible container, against which a user can grasp and squeeze the flexible container for mixing or drinking Optionally or alternatively, a mixing element is suspended by the support element(s). The mixing element impinge upon at least a portion of fluid within the container to create turbulence, thereby promoting mixing of powdered material disposed within the container.