Albert Barnes Commentary 1 Samuel 14:27

"But Jonathan heard not when his father charged the people with the oath: wherefore he put forth the end of the rod that was in his hand, and dipped it in the honeycomb, and put his hand to his mouth; and his eyes were enlightened." — 1 Samuel 14:27 (ASV)

Were enlightened - that is, he was refreshed when he was faint.