How do i get a plastic bottle cap out a bottle cup sized hoover tube?????

Have you tried blowing it out. Wipe the opening on the opposite side of the tube where the cap is with some rubbing alcohol till it's clean and let dry. Then take a deep breath and blow through the tube, sealing the tube by pressing it against your face. This should dislodge the cap enough to where you should be able to shake the cap out.