Yank Tank is a slang term which has two meanings.
Classic American cars in Cuba
Yank tank or máquina are the words used to describe the many classic cars present in Cuba. After the Cuban Revolution, the U.S. imposed an embargo on Cuba, making direct imports/exports between these two nations very difficult. Under Cuban communist rule (1959-present) ownership of any post-1959 car requires a state permit and the vehicle must be given to its partial proprietor directly by the Cuban state. During the years of Soviet Union influence on Cuba, Ladas, Moskvitchs and Volgas became the main cars imported by the communist regime, mainly for state use. As a result of these internal economic restrictions, until this day there is also no such thing as a new or used private European or Asian automotive dealership branch in Cuba for independent purchasing by normal Cubans.
As a result, the only cars that could be purchased freely ("particular" plates) are those that were previously registered for private use (acquired before the revolution) and a small number of used vehicles dropped out from local authorities. So cars that were present, mostly American, were nurtured. And since there were many of these, due to the presence of a past strong Cuban middle-class, classic cars have been the standard, rather than an exception in Cuba. Due to the constant good care, many remain in good working order.
However, many of these vehicles, especially those in taxi service, have been converted to accept replacement engines. The practical limits of engine longevity, scarcity of replacement parts, and the high cost of fuel in post Cold War Cuba have made diesel power a popular choice for engine replacement.
American Cars in Great Britain
The term "Yank tank" is also used in Australian and British slang to describe these cars, but more generally to describe any American car considered to be large and unwieldy - including both classics (such as Cadillacs) and modern SUVs. The term entered the general vocabulary in Britain during the Second World War and especially the decade afterwards, when some American servicemen stationed in Britain imported cars from the USA. This happened at a time when American cars reached their largest sizes and most extravagant styling, leading to the term 'Yank Tank' in relation to these cars' bulk and unwieldy size on typically narrow and winding British roads. This difference was especially great because British cars of the 'Austerity Years' in the late 1940s and early 1950s were generally small, low-powered, with low equipment levels and constrained styling in comparison.