Was Cain growing drugs? Did this anger God? The numismatic evidence.
Obviously we have do not have numismatic evidence from the time of Cain and Abel. We do have clear numismatic evidence from antiquity and the Bible of the first crops cultivated and harvested for human use. Lets just assume Cain was growing grapes, barley, and opium poppies which are the most frequent agricultural products shown on ancient Greco-Roman coinage. These are products that Cain may have brought before the Lord as a sacrifice. God was clearly unhappy with the actual product of the sacrifice as well as the condition of Cain's motives.
Noah planted a vineyard after the Flood and became intoxicated. The mental state of Adam, Eve, Cain and Abel must have been similar after the expulsion from the Garden. Harvesting plants that alter the mental state in a way to separate God's children from God would not make Him happy. Not to mention how Cain reacted and killed his brother is a sign of a completely dysfunctional or reprobate mind. Was Cain intoxicated when he killed his brother? For those who have read my prior posts showing the opioid imagery on the coins of Herod the Great it is very easy to see the connection in the Biblical narrative. Josephus blamed the Great Revolt against Rome on "unreasonable hatred." Yep "bad plants" have always been the problem. Maybe that's the reason for the Garden of Eden in the first place.