Hydroxychloroquine is an anti-malarial. I thought he took Adderall.

What makes you think he isn't simply lying about taking it? It's not as if it would be against his principles (as if he had any).

Motive?

To promote the product in which he has a financial interest, and most of all, to give himself more credit (stable, genius) for intuitive medical acumen which has now been shown to keep him well even without use of mask.

All of which give him both financial and political (election) profit motives.