Its not possible to drop an item from a container to the ground or to destroy it by dragging it out of it. I stored grass in a container, then wanted to pick up the container but it said it needs to be empty. So I tried to drag the grass to the ground as I usually do when its in my backpack, but it did nothing, no message, it simply stayed in the container. The only way to empty it was to drag the grass from the container to my backpack.