To defeat the Breadbug much more quickly, instead of having him get sucked in two times, just do it once and finish him off with Captain Olimar.

Instead of throwing Pikmin at it, have a pellet fall near him. He will try to get it. Assign two Pikmin (prefably flowers) to the pellet that it is carrying. They should start a tug of war. If they get to the Onion, the Breadbug will be sucked up, losing almost all of its health. Do this once more and it will be defeated, allowing you to claim your prize (the Space Float).