Mario & Luigi: Superstar Saga
It is only mentioned in the game. Chuckola Cola is said to be a sweet-smelling soda produced in Chateau de Chucklehuck, but cannot be obtained in-game.
Paper Mario: The Thousand-Year Door
In Paper Mario: The Thousand-Year Door, Admiral Bobbery wanted a Chuckola Cola as his last request. He said he saw a bottle of it wash up on the beach, and asked Mario to go and get it. When Mario asked Flavio about it, Flavio told him that he could have the Cola only if he could find something to replace it, as it was a vital part of their food supply. Mario then found a coconut, which Flavio deemed an acceptable replacement. Mario then took the Cola to Bobbery, who drank it. However, Bobbery soon realized he wasn't dying, and therefore agreed to help Mario in his quest for the Crystal Stars.