God instructed them to be fruitful and multiply in chapter one of Genesis.
God blessed them and said to them, "Be fruitful and increase in number; fill the earth and subdue it. Rule over the fish in the sea and the birds in the sky and over every living creature that moves on the ground." Genesis 1:28
It was not until chapter three of Genesis that they disobeyed and ate of the one tree that was forbidden them. Fruit is used as a metaphor many times in Scriptures. For instance, as Christians, we are to bring forth good fruit. We are even told how to do this.
The fruit we are to bear has different aspects to it. One is character building: the fruit of the Spirit is love, joy, peace, patience, kindness, goodness, faithfulness, gentleness, and self-control. Against such things there is no law.
Peter adds to this: make every effort to add to your faith excellence, to excellence, knowledge; to knowledge, self-control; to self-control, perseverance; to perseverance, godliness; to godliness, brotherly affection; to brotherly affection, unselfish love. For if these things are really yours and are continually increasing, they will keep you from becoming ineffective and unproductive in your pursuit of knowing our Lord Jesus Christ more intimately.
So our life surrendered to God, and our works through faith are fruit, and so are people who come to Christ through us (Rom 1:3; Phil 4:17), and there is also the fruit of our lips as we praise God and witness to others (Heb 13:15).
These are good fruits, partaken of when aligned with the will of God.
Evil fruits would be the result of disobeying God, defying God, following self will in opposition to God's will, severing ourselves from fellowship with Him, etc. That is the fruit Adam and Eve bore and ate (lived). They followed the lusts of the flesh (not meaning sex) and the desires of the eyes and pride of life, in turning away from God after being in fellowship with Him. It is what we all do before being regenerated by the Holy Spirit of God.
