You cannot legally download the FIFA 16 PC demo today. Your best bet is to buy the full game cheaply (e.g., via a used key from a reputable seller like Green Man Gaming or Amazon), or play a newer FIFA demo (FIFA 23 or EA Sports FC 24 have demos on Steam/EA App).
I couldn’t find a direct, official article from EA about a "demo FIFA 16 PC download" because for that game. The game was released in 2015, and its demo was removed from official stores (like Origin, now EA App) years ago. demo fifa 16 pc download