Complex sentence: Malted milk was originally manufactured as an artificial infant food, but became better known in the USA as the basis for malted milkshakes, which were invented in 1922 by a soda jerk at a Walgreens drug store in Chicago.
Split into simpler sentences: Malted milk was originally manufactured as an artificial infant food. It became better known in the USA as the basis for malted milkshakes, which were invented in 1922 by a soda jerk at a Walgreens drug store in Chicago.