Coatings are provided to give polymeric structures a top coat that improves the gas barrier properties of the structure while enhancing the water resistance of the top coating and while improving the adhesion of the top coat to an underlying layer of the structure. These top coat compositions comprise an organic barrier coating material in combination with an epoxide additive which enhances the water resistance, adhesion, gas barrier, or a combination thereof, of the top coat barrier layer. Multilayer structures having this top coat are also provided, particularly in the form of containers for food and beverage packaging.