Blue Boxes can be broken by running into them, Quick Spinning into them, or attacking them with an ability. The higher the machine's offense, the less hits it takes to break them. Likewise, the more speed a machine has when touching the box, the more likely it will break upon contact.
The Blue Box also reappears in the Kirby Fighters sub-game of Kirby: Triple Deluxe (as well as the downloadable Kirby Fighters Deluxe and its sequel Kirby Fighters 2). The boxes can be destroyed to uncover items.