If you're struggling with the game then activate the following effects to make the game easier by entering the code for the effect you want at the 'Cheat Code' screen on the upgrade computer at the bottom of the Magwu Lair.
Attract Coins (Makes them Easier to Collect): Enter Tralok, Plankton, Danny, Plankton, Tak.
More Gadget Combo Time: Enter Spongebob, Beautiful Gorgeous, Danny, Plankton, Technus.
Goo Doesn't Slow you Down: Enter Danny, Danny, Danny, Technus, Technus.
Don't Lose Coins when you get Knocked Out: Enter Plankton, Jimmy, Beautiful Gorgeous, Jimmy, Plankton.