Sugar
From Tardis Wiki, the free Doctor Who reference
Sugar is a natural sweetener found on the planet Earth. It can be added to drinks like coffee and tea.
In 1963, the Doctor chatted with John about how tea with sugar was different from tea without sugar. (DW: Remembrance of the Daleks)
In the 1970s, the Doctor stopped the Multi-Mobile by putting sugar cubes in its petrol tank. (TVC: The Multi-Mobile)
In 2070, the Cybermen poisoned the sugar in the Gravitron's employees' coffee. (DW: The Moonbase)
