If you have money to spend here are some ideas:

• multicopters flight in field of vision or FPV
• RC cars, there may be some RC race tracks around big cities
• if you have some sea or lake nearby, windsurfing might be good idea
• photography

More cheap ones

• find some hackerspace or maker groups, they usually understand that someone needs less social interaction, and you can learn to build stuff
• bird watching
• ingress mobile game (or any other made by niantic)