Keeping the World Safe from Hydration

Why is it that I can attend a Washington Nationals game and bring in food and water yet when attending a Washington Capitals game, such items are prohibited?
Obviously, people bringing in food affects their food sales.
An usher gave me the usual “security” malarky as an explanation. If I’m a security risk because I’m bringing in a 20 oz container of water, then that Dasani truck driver must be on the ten most wanted list.