Disclosed is a pack. The pack includes a pack body in which fluid is receivable, a plug affixed to an inner surface of the pack body, a portion of the plug being configured to protrude outward from the pack body, the plug having a discharge opening perforated therein, a lid located at one side of the plug to close the discharge opening, and an elastic member located at one side of the plug to impart elasticity to the lid in a direction of closing the discharge opening.