I addressed this question in considerable detail in this essay here.

The tl;dr is that the Ottoman sultan, Abdülmecid I, learned of the famine via his Irish physician, Justin McCarthy, who had been born in Cork. We have no sources from the Ottoman side to tease out his precise motives for offering the £2,000 donation he made to the main private fund for famine relief. There seems no reason to suppose it was not simple charity on the part of a ruler who had no other direct links with Ireland at all.

A related story, which discusses the arrival of three shiploads of food send by the Ottomans, appears to be a legend that has at its basis the arrival of several cargoes of maize sent to Drogheda that had loaded in Thessaloniki, then an Ottoman-controlled port. Details uncovered from contemporary Irish newspapers suggest these cargoes were intended for sale, however, as they were consigned to local Irish merchants, not handed over to any relief organisation.