Shake Shack is reportedly launching its first loyalty program after completing a successful test earlier this year.The fast-casual restaurant chain began offering $1 sodas on Wednesday (May 28) to customers who place orders through its app or online and will launch an offer on June 5 that gives discounts to those who place at least two orders online or on the app within a specified time, Bloomberg reported Wednesday.The company will expand its new loyalty program later this year, according to the report.Sha ...