There are no cheat codes directly available in "Wii Play: Tanks!", but the game can be modified by using a third-party cheat manager. To enable these cheats, install Gecko Cheat Code Manager on your PC, and use that to upload cheat codes to an SD card for your Wii.
Accessing the cheat codes on your Wii requires the use of the Homebrew Channel. Install the Gecko app on your Wii, and follow the instructions. Be sure that SD Cheats is enabled in Gecko's settings. The codes must be initially loaded onto the SD card using your PC before they are available. As of 2014, a list of codes for Wii Play, which allow effects such as enabling infinite tank lives and setting the high score, is available at the GeckoCodes website.