Mindy loves empty water bottles. I had forgotten how much until I listened to Tara and Walter’s K9Cast #25 and was reminded.
But instead of a plain empty bottle, I add some of Mindy’s kibble into the bottle, and this keeps her busy for a few minutes (like the kongs) as she tries to spin and turn over the bottle to get the food.
Once the food is gone, I can add more, or just let her play with the empty bottle.
I find the thicker plastic bottles work better. For example, Glaceau Fruit Water bottles are a little more rugged for heavy chewers. Mindy is small, but she can chew like the big dogs, so we need durable toys.
And we watch her very closely, since the bottle can start to tear or break off little pieces. We remove the bottle when that happens. 
