Go to an area where you can catch a fish with a bottle. Equip a bottle to one of the C buttons. Press the button you put the bottle on and it will swipe at the fish. Before you catch it press start and bring up the "iteam select" screen. Select an item you dont need (i.e. claim check) and equip it to the button where you had the bottle before. NOTE: Do NOT select an item you need! You will NOT be able to get it back!