Who doesn’t like the chance to win something? Using a sweepstakes to prompt email signups is extremely effective. It’s highly recommended that the prize be your product or something related to discourage sign ups who will be unengaged and who will likely in time unsubscribe, or worse yet, report your emails as spam.
Try partnering with a like or similar but non-competing brand and do a co-branded sweepstakes to expand your reach. You must mind your legal p’s and q’s when developing and promoting your sweepstakes, so make sure your lawyer or legal department goes over the details.