Yes, you can win money at Fliff, provided that you are in one of the states that permits wagering with Fliff Cash. After you wager it once, you can redeem Fliff Cash for real money (at a 1:1 ratio). There is a minimum withdrawal requirement of $50.
While you can make real money via the cash prizes on Fliff, this is merely as a part of the promotional sweepstakes. Because Fliff doesn't feature any form of real money gambling, it is legal in way more states that you get with regular online sportsbooks.