You will reach a room with two levels, each floor with two goons on 
them. First, take out the goons. Then, look around on the lower floor 
until you see a sewer pipe with boxes in the sewage. Carefully glide 
down and land on the first box. Jump over the next few boxes and pick 
up the envelope with an "E" on it. Finish the game and the "Infinite 
Health" cheat will be unlocked.