A sweepstake is a type of contest where a prize or prizes may be awarded to a winner or winners. Sweepstakes began as a form of lottery that were tied to products sold. In response, the FCC and FTC refined U.S. broadcasting laws (creating the anti-lottery laws).
Yes it is permissible as far the business is lawful.
If the prize is provided by the money collected from the message rate, then it would be a gamble and is not permissible.