Likely answer

The Warrior Kid Book by Jocko Willink

The query "The warrior kid" refers to "Way of the Warrior Kid" by Jocko Willink. First published in 2017, this motivational children's novel follows a young boy who learns self-discipline, confidence, and fitness over summer break with the guidance of his Navy SEAL uncle.

Confirmed match: Way of the warrior kid by Jocko Willink