Complex sentence: He also explains that a handkerchief in package contained the scent of rabbit blood and cocaine, to attract the dogs so when they sniffed it, the cocaine would temporarily numb the German dogs' sense of smell.
Split into simpler sentences: He also explains that the handkerchief in her package had a scent of rabbit blood to attract the dogs, and it contained cocaine. When the German dogs sniffed it, the cocaine would temporarily numb their sense of smell.