Jake couldn't tell Clara that their sponsorship contract would have to end this season, it was not yet final and Jake had only told his mother for now, so it was better than Clara could have great sales this year because next year they would not have it to help improve sales.
Jake could say that he would join the NBA only after the end of this basketball season when he had no problem that nobody knew about, the companies that negotiated with David knew that Jake would enter the NBA, but they would never say anything about it so as not to spoil their reputation.
If in the future Jake could help Clara's company in any way even if he didn't receive sponsorship he would help, the problem was that his future contract with the shoe company would probably prevent him from doing so.