A drink common among the dodgier elements of the Cape Town population.
One makes a blue train by filtering methylated spirits through a loaf of bread in order to remove the bitter-tasting purple dye (In South Africa, the dye is mandatory in order to prevent it's use as a beverage). Since only the dye is removed, not the kerosene, methanol, isopropanol etc, it gets you smashed off your head, but may cause vomiting, headaches, seizures, blindness and/or death.
It is called blue train because the thoroughly dyed loaf resembles the Blue Train, an ultra-luxury overnight passenger train between Joburg and Cape Town.
Dave's actually started drinking blue train. Now that's a rock-bottom alcoholic!