When he was 30 years old, he worked at a German subsidiary of Coca-Cola in 1933. Sales of Coca-Cola in Germany rose from 100,000 cases in 1933 to over 4 million cases in 1939. Because of the Allied blockade, Coca-Cola GmbH was unable to get Coca-Cola syrup during World War II. The supply of regular Coca-Cola ran out in 1942. To keep the plant in operation, Keith developed a fruit flavored drink made from apple fiber, left over from cider pressings, and whey, a byproduct from cheese manufacture, creating Fanta.