A codename for weed/Marijuana/Cannabis.
One day, two high friends were at one of their houses. One of them saw a bottle of Canada Dry, and attempted to say it. The friend, being quite high, mis-pronounced it, saying "Cananada Dry", and thats how the term Cananada Dry came around.
Bob: Hey man you wanna drink some Cananada Dry?
Joe: Get high man? Heck yes!