
Pineapple cordial is a sweetened pineapple concentrate with acid in it, so it brings sourness along with the sugar.
Pineapple juice reduced with sugar and finished with a little citric acid or lime gets there — the acid is the half that makes it a cordial. Pineapple liqueur carries the flavor and adds alcohol, so the drink needs rebalancing for strength as well as sugar.
Pineapple syrup
Pineapple cooked down with sugar and nothing sour added; it sweetens and does not sharpen, so a tiki build wants its lime kept up.
Pineapple liqueur
Alcoholic, drier, and it will not carry the sweetness the recipe expects from a cordial; useful when the drink can take the extra strength.
Pineapple carries wild yeast and its own enzymes, so this is the cordial most likely to start working in the bottle. Refrigerate it, use it within a fortnight, and do not seal a warm batch tightly — pressure builds.