there is one cheat i know of...
play suduko on medium and then at the end, right before the board goes grey and it says you've completed it, click the hint button, then the board will go grey, click the hint button again and you should get i think around 1600 point and 1000 millsbucks. some people who do it also say you can get trophies, but i donno if thats true because i already had a trophie for the game when i found this hint, and your score doesn't show up in the top scores board. but you do still get 1000 millsbuck instead of 550, and that will add up fast