Things You'll Need
Instructions
Choose the "Brawl" option and start a multiplayer game with any character.
Tap on "2 minute KO fest" to change the game settings. At the item screen, turn off every item except for the pokéball (it's the third item in the top row).
Play the "Brawl" game with any other settings you want. If you choose "Man survival test" you'll be able to throw as many pokéballs as you want without worrying about a time limit.
Grab pokéballs as soon as they appear and throw them. Kyogre will eventually appear, but it may take some time since it is a rare Pokémon.