The fruit Jesus is referring to in John 15 is to love God with all your heart, soul, and mind, and to love others.
“If you keep My commandments, you will abide in My love; just as I have kept My Father's commandments and abide in His love.”
JOHN 15:10 NASB
I believe in Matthew 25:31-46 the goats were condemned because they did not love others. Notice the examples given in verses 42 & 43. They are all pertaining to love for others.
“"Then He will also say to those on His left, 'Depart from Me, accursed ones, into the eternal fire which has been prepared for the devil and his angels; for I was hungry, and you gave Me nothing to eat; I was thirsty, and you gave Me nothing to drink; I was a stranger, and you did not invite Me in; naked, and you did not clothe Me; sick, and in prison, and you did not visit Me.'”
MATTHEW 25:41-43 NASB
James gives similar examples in James 2:15 & 16 in reference to verse 14 when he said can that faith save him? Indicating that a faith without works of love is not a saving type of faith.