The term 'SOFT-DRINK BUY' can be broken down into two crossword solutions: CASE (4 letters) and LITER (5 letters). CASE is a term used to describe a unit of measurement for a quantity of items, usually referring to a box or container. It is often used in the context of retail, such as when purchasing a CASE of soft drinks. LITER is a metric unit of volume, equal to one cubic decimeter. It is commonly used to measure liquids, such as a liter of soda.