The food item you are describing is “malt vinegar.” It is a type of vinegar that is clear and colorless, with a rather strong flavor. Malt vinegar is made by distilling malted barley, rather than using cider or wine as a base. It is a common condiment in many parts of the world, particularly in the United Kingdom, where it is often used as a topping for fish and chips. Malt vinegar is also used as an ingredient in various recipes, such as marinades and sauces.