Do they offer spring soccer where you live? It's probably too late to sign up for this year if they do, but it's something to keep in mind for next year if they still enjoy soccer.
A lot of kids in our community take classes once a week or so after school. We have great offerings for things like art, computer programming, minecraft, Lego engineering, foreign languages, and so much more). Do you have a local community center, YMCA, art studio, or STEM center that offers any extracurriculars?
My kids usually spend anywhere from 30-60 minutes playing together at home after school. We try to have a play date once a week, sometimes for both of them and sometimes for just one. I know you said a lot of kids go to after school care - could you work something out with any of the parents where you take the child home with you after school one day instead? Our school's day care center will allow this if it is pre-arranged with the child's parent.
Other options include going to the park, riding bikes/scooters, playing outside with a ball, etc.