Serving inventive drinks to a cocktail-savvy clientele at its outposts in New York, Paris, and London, Experimental Cocktail Club has taken on an enormous challenge in opening its fourth location on the Spanish island of Ibiza, the land of vodka and Red Bull. But its expert mixologists are up to the task: One of the more exceptional offerings is a spin on the classic Italian Aperol spritz that uses an Aperol infused with vanilla.