Fischer, who once worked on an Opel assembly line and was one of the early leaders of the environmentalist Green party, is advising the firm on developing a sustainable and environmentally friendlier business strategy, according to Der Spiegel news magazine.
BMW isn't the only blue-chip client for Fischer's consulting business, which will open a new office in Berlin this fall. The former street brawler has also worked with the energy firm RWE and the Nabucco natural gas pipeline project.
According to Der Spiegel, BMW hired Fischer because his extensive international experience while serving as foreign minister from 1998 to 2005 makes him a rich source of ideas and one of the world's experts on sustainability.
Fischer's work with BMW is not his first foray into the automotive business. During the 1970s, he worked on the assembly line at an Opel factory in Frankfurt trying to organise workers. Fischer also spent several years behind the wheel of a taxi before joining the Greens in the early 1980s and becoming one of the first Green members in parliament.
He caused a scandal when he wore a pair of sneakers while being sworn in as a member of the Bundestag in 1983.