liqueur

likööri A flavored alcoholic beverage that is usually very sweet and contains a high percentage of alcohol. cordial Cordials are a type of liqueur manufactured using the infusion process as opposed to the essence and distillation processes.
to flavor or treat (wine) with a liqueur
to top up bottles of sparkling wine with a sugar solution

Every champagne has to be liqueured after its disgorgement, to replace the inevitable loss.