-To defeat the Breadbug faster finish him off after the first time it gets sucked into the Olimar with your Pikmin instead of waiting for it to get sucked in a second time.
-Instead of throwing Pikmin at it, have a pellet fall close to it. It will try to carry it away. Assign two Pikmin (preferably flowers) to the pellet that it is carrying away. They should start a tug of war and drag the Breadbug to the Onion, where it will be sucked up and lose almost all of its health. Do this again to kill it, allowing you to claim the Space Float.