You just need to try things until you find something you keep going back to. Examples of hobbies:

Exercise (running, crossfit, weight lifting, parkour, tabita, yoga, hiking, biking)

Sports (rock climbing/bouldering, soccer, baseball, basketball, autocross/road racing, roller derby, surfing, archery, sailing)

Martial arts (aikido, thai boxing, brazilian jiu-jitsu, tai chi, capoeira, kendo, eskrima/arnis, krav maga, fencing)

Dancing (salsa, merengue, swing, tango, blues, ballroom, hip hop, jazz)

Music (learn an instrument, live local shows, discover new genres, download and listen to new music)

Literature (join a book club, cheap books from thrift stores or yard sales, try fiction/nonfiction, reflect on what you read, blog it)

Blogging (research and then write about a subject you care about)

Volunteerism (soup kitchens, community gardens, local government, special needs, peace core, hackerspaces, free education community organizations, conventions, public awareness, public services, community programs)

Weird stuff (slacklining, acro-yoga, aerial silks, unicycling, juggling, rope bondage, home brewing, crafting, building models, puzzles, trivia, ham radio, blacksmithing, astronomy, woodworking, car tuning, karaoke, magic, gravestone rubbing, gardening, canning, locksport, leatherwork)