When you first start the game you notice that if you go on Pro Career and go right to the end, there is a Honda Championship. You can do what 'teddybear_jacko' said and go to the website, but last time I went on there it gave me a serious Virus, which then resulted into me getting a new computer. But another way you can get it is to finish world tour mode. If you think it will take too long, then go on to the action replay section. I submited a load of action replay codes, but the one to help you is the 999 points one. You only have to go into the race and retire straight away, and you'll get 999 points. Of course you can just put in the action replay code for the Honda Championship but then you won't unlock different sports as you go through world Tour.
In the honda championship there is a Lawnmower challenge where you race Lawnmowers!