Complex sentence: The dress code required jackets for men and was strictly enforced; a man who arrived with a reservation but without a jacket was seated at the bar.They also had jackets that were loaned to the patrons so they could eat in the main dining room.
Split into simpler sentences: The dress code required jackets for men and was strictly enforced; a man who arrived with a reservation but without a jacket was seated at the bar. The restaurant offered jackets that were loaned to the patrons so they could eat in the main dining room.