Fast-food chain Sonic (NASDAQ:SONC) this week unveiled an increase to its stock repurchase program. Under the latest authorization's terms, as approved by Sonic's board of directors, the company can repurchase up to $40 million of common stock through Aug. 31, 2014.

Prior to the most recent increase, Sonic's board had authorized a $55 million share repurchase in January 2013, and currently has about $18.4 million remaining from that program. According to CEO Clifford Hudson, the company's franchise business model continues to generate "significant free cash flow." During 2013, Sonic has seen its price per share rise from $10.41 to $15.89 at yesterday's closing, a 53% increase.

Sonic has more than 3,500 drive-ins serving 3 million customers every day.