The Notorious Barksters silicone collapsible dog bowl does all the good dog bowl things - holds water, holds treats, collapses for easy storage and portability, and comes with a carabiner to clip wherever you want. Ideal for woof conditions.

The opening is ~5 inches across, the base is ~3.5 inches across, and the expanded height of the bowl is ~2 inches tall.  According to the math I definitely know how to do, this dog bowl will hold a good ass amount of water.