The other toys - the milk pack

Is it because he is an ex-street dog that he is so attracted to anything trash related? The second most fun thing to chew on, or rather in this case to completely shred to pieces, is a milk pack. The concept is the same as for the water bottle (chew the cap off, decide between the cap and the milk pack body) and once he's done with it there really isn't much left. Except that I need to clean up.