Sonic Drive-Ins has a simple strategy for adding $45 million a year in revenue: close the gap between company-owned restaurants and franchisee units. Average unit volume at Sonic franchisees is about $1 million a year, Sonic CEO Cliff Hudson said on a conference call this afternoon. By comparison, company-owned units make $900,000 a year. If Sonic can close that gap by bringing unit volume at those 452 company units to $1 million, that would add a total of $45 million to company revenue a year. Of course, to do that, Sonic has to reverse a same-store sales slide that coincided with the onset of the recession, and while comp sales have been improving, they still remain in negative territory (they were down 2.4% systemwide last quarter). Yet Hudson said on the call that closing the gap is "very achievable."