Sweeps coins can only ever be obtained as a cost-free bonus and can never be bought. https://cirandas.net/simonmoody/blog/%EC%B9%B4%EC%A7%80%EB%85%B8%EC%82%AC%EC%9D%B4%ED%8A%B8-%EC%95%88%EC%A0%84%ED%95%9C-%EC%98%A8%EB%9D%BC%EC%9D%B8-%EC%B9%B4%EC%A7%80%EB%85%B8-%EA%B2%8C%EC%9E%84%EC%9D%98-%EC%83%88%EB%A1%9C%EC%9A%B4-%EC%8B%9C%EB%8C%80