FishVille has players swapping Super Grow and Caffeine for Sand Dollars
When you log-in, you should get a pop-up notice that'll allow you to cash in your leftover Super Grow and Caffeine for Sand Dollars. Five Super Grows or six Caffeine should net you 1 SD each. You can keep using your Super Foods until May 25th, but after that, these items will be disabled. They've already been removed from the game store and gifts page.