Fruitcake was a kind of cake that originated on Earth.
The Fourth Doctor told Jack Tyler to bring him four cups of tea and some fruitcake, stating, "I love fruitcake". He did this to create an everyday scene with which to bring Martha Tyler back into normality.
When the Eighth Doctor and Charley Pollard first arrived in the Divergent Universe, he temporarily convinced her that she could detect the smell of fruitcake, when in fact there was no smell at all. (AUDIO: Scherzo)