Are you kidding me? EDC a water bottle? C'mon. Of course. I use 1L Nalgene bottle with a variety of lids and tops, summer is mostly wide tops for adding ice.

There is a photo of the Nalgene Flask on the first page. My son uses it. As I used it, the external cup was really good for the hip pouch of my pack. When it was seated hard in the pouch, I could pull the flask out and the external acted as a holster so I wouldn't have to wedge it back in.

The double cap on top served two purpose. Internal is a cap for the flask. The larger blue cap you see in the picture unscrews and acts as a 1 oz shot glass.