Jonas lives in a tightly controlled society. Unlike most kids his age, he is not focused on one hobby. He does a little bit of everything.
Hobbies as we know them don't exist in Jonas's world, but they do have volunteer hours.
As part of Jonas’s training, he has to volunteer in several different professions. Jonas does not choose one. Instead, he seems to enjoy spreading his volunteer hours around, doing a little of this and a little of that.
The freedom to choose where to spend those hours had always seemed a wonderful luxury to Jonas; other hours of the day were so carefully regulated. (p. 26)
Like most kids, Jonas plays ball and rides his bike. These are not hobbies though. He plays catch with his friend Asher because it is required exercise to help his hand-eye coordination.
Jonas was glad that he had, over the years, chosen to do his hours in a variety of places so that he could experience the differences. (p. 29)
If Jonas has any actual hobby, it would probably be hanging out with Gabe. He consoles Gabe and takes care of him, and even gives him memories—even though it’s forbidden.
Lowry, Lois (1993-04-26). The Giver (Newbery Medal Book) (p. 26/29). Houghton Mifflin Harcourt. Kindle Edition.