Christophe Fauviau, who confessed to the crime, told the court he was responsible for Alexandre Lagardere's death and that "I'll always carry that with me".
"Not for one second did I think of hurting people. I realise now that I did," the 46-year-old former military pilot said.
Fauviau was accused of spiking the water bottles of his children's opponents 27 times in tournaments across France from 2000 to 2003. He used the anti-anxiety drug Temesta, which can cause drowsiness.
Prosecutor Serge Mackowiack had asked the court to sentence Fauviau to between eight and 10 years in jail.
The maximum for the charge of unintentionally causing death by administering toxic substances is 20 years.
Mr Mackowiack said Fauviau had been a good soldier and said he did not seek to kill or injure the players.
Still, the prosecutor described Fauviau as "an adult who turned his children into objects of his own fantasies of success" and whose actions were premeditated.
"Nothing stopped you: Players collapsing on the court, the sight of stretchers, of an 11-year-old girl, a young woman who collapses against a fence. Nothing stopped you," Mr Mackowiack told the court in Mont-de-Marsan in south-western France.
Fauviau's 16-year-old daughter Valentine is a rising star in French tennis. In tearful earlier testimony, Fauviau asked Mr Lagardere's parents for forgiveness.
Opponents of Fauviau's daughter Valentine and son Maxime complained to investigators of various ills: weak knees, dizziness, nausea or fainting. Several were hospitalised.
In July 2003, Maxime Fauviau defeated Mr Lagardere, who complained of fatigue after the match and slept for two hours.
While driving home, the 25-year-old school teacher crashed his car and died, and police believe he fell asleep at the wheel. Toxicology tests showed traces of Temesta in his system, delivered by Christophe Fauviau.