The modern improvement for an age-of-sail crew

What modern innovation would best improve an age-of-sail warship without compromising its fighting role?

A proper galley kitchen would improve food preparation, professionalize cooking, and improve sanitation aboard ship.

The answer deliberately resists spectacular choices such as engines or electrification and selects the galley. A proper kitchen improves food quality and makes cooking a professional shipboard function. It also gives a cramped wooden warship a significant sanitation improvement. The answer demonstrates that combat endurance can depend on ordinary domestic systems that keep a crew healthy and fed as much as on an obvious weapon or propulsion upgrade.