I checked with a flight attendant, who looked it up in their manual. The policy for domestic flights in coach is to pour the beverage into a cup with ice, and only give the can upon request. The exception to this is Shuttle flights, where they offer the can unopened with a cup. If the FA's are telling you they can't give you the can, they are lying. Write it up. These FA's that just make up their own rules really irritate me.