It's too rare for such things unless you get it from offerings or some deals coming from reviews but mostly they aren't free bet but just some bonuses if you sign up or something. Most case if it's a new sportsbook site then I guess there's a huge possibility that they may offer free bets. There's some games you can find on Games and Rounds board though especially for sportsbet.io but mostly this is just prediction game but you'd be getting rewards if you hit it.