Sonic's (NASDAQ:SONC) stock has sizzled in the past few weeks. After bottoming out around $27.50 in mid-January, it has climbed roughly 27%, trouncing the market's return over that short period. A look at the company's latest results may explain investors' enthusiasm.

Second-quarter earnings per share soared by 22.2%, to $0.22. The bottom line benefited from a share-buyback program that decreased the company's weighted average share count by roughly 5%. On top of this, Sonic saw a 12.3% increase in net sales, supported by a 5.5% increase in same-store sales and the acquisition of 15 formerly franchised units.

CEO Clifford Hudson attributed Sonic's solid sales performance to new product offerings and a more aggressive advertising campaign. Sonic has begun pushing more health-conscious menu items, including new salads topped with grilled chicken and a low-calorie diet cherry limeade. Additionally, it's boosted sales by adding credit card terminals at each drive-in station, a program it calls PAYS.

In the quarters ahead, the company will continue to focus on these three initiatives to fuel continued growth. Currently, 60% of franchise drive-ins have the PAYS program implemented; plenty of opportunity remains as the remaining sites come onboard.

Sonic will open another 180 to 190 units in 2006, up from 175 new drive-in developments in 2005. The company's healthy free cash flow will be used to cover the capital expenditures of this expansion. In addition to funding unit growth, its free cash flow is also being used for share repurchases. For the remainder of 2006, the company has $35 million budgeted for potential stock buybacks.

All told, things look downright savory for Sonic. I was impressed with this operation back in October 2005, and little has tempered my enthusiasm since. After the recent run-up on its stock, prospective investors may want to wait for some weakness before hopping on board - the company is currently trading at 27 times trailing-12-month earnings, compared to a long-term expected growth rate of 17%. That said, Sonic is charging ahead at full speed, so waiting for 2006 lows to return may be a futile endeavor.

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Fool contributor Jeremy MacNealy does not own shares of any companies mentioned.