The phrase "drink flat" is often used to describe a carbonated beverage that has lost its fizz. There are several synonyms for this phrase that people use in everyday language. Some of the common synonyms for "drink flat" include "flat soda," "stale pop," and "boring seltzer." In some regions, people refer to such drinks as "dead soda" or "dead pop." Regardless of the phrase used, it is clear that these synonyms refer to a carbonated beverage that has lost its characteristic bubbles and effervescence. While flat drinks may not be as refreshing as their carbonated counterparts, they can still be enjoyed for their flavor.