barley water
From Longman Dictionary of Contemporary Englishbarley waterˈbarley ˌwater noun [uncountable] British English a drink made from barley boiled with water, with the flavour of lemon or orangeExamples from the Corpusbarley water• The meal then followed and all had their fill of sausage rolls and crisps, washed down with delicious barley water.• It was as if he had returned to the pavilion to celebrate with lemon barley water after a half-century.