Looking for some cheap food in December as you run around shopping like crazy? This weekend, Subway is out with a December promotion for a $2, six-inch sub sandwich. The $2 sub deal is good only on its popular meatball and cold-cut subs. Beating its own $5 footlong promotion, Subway joins several other major fast food chains dabbling this year with $2 meals — including Taco Bell, Chipotle and some regional KFCs. December is typically a slower month not just for Subway but for the entire fast-food industry. The Subway deal is the lowest-price 6-inch sandwich that the chain has offered in years, says Tony Pace, marketing chief at Subway’s franchisee advertising fund.