The Prophet ﷺ said: When one of you is fasting, he should break his fast with dates; but if he cannot get any, then (he should break his fast) with water, for water is purifying.  

قَالَ رَسُولُ اللَّهِ ﷺ إِذَا كَانَ أَحَدُكُمْ صَائِمًا فَلْيُفْطِرْ عَلَى التَّمْرِ فَإِنْ لَمْ يَجِدِ التَّمْرَ فَعَلَى الْمَاءِ فَإِنَّ الْمَاءَ طَهُورٌ  

The Messenger of Allah ﷺ used to break his fast before praying with some rutabah dates; but if there were no rutabah dates, he had a few fully ripened dates, and if there were no fully ripened dates, he took some mouthfuls of water.  

أَنَّهُ سَمِعَ أَنَسَ بْنَ مَالِكٍ يَقُولُ كَانَ رَسُولُ اللَّهِ ﷺ يُفْطِرُ عَلَى رُطَبَاتٍ قَبْلَ أَنْ يُصَلِّيَ فَإِنْ لَمْ تَكُنْ رُطَبَاتٌ فَعَلَى تَمَرَاتٍ فَإِنْ لَمْ تَكُنْ حَسَا حَسَوَاتٍ مِنْ مَاءٍ