What is the best way to maintain 100 battery capacity for IPhone 14 Pro?

To learn about maximizing battery life and lifespan, read this support document --> Batteries - Maximizing Performance - Apple

Click on this link about Phone battery and performance to read about the battery health feature and what is considered normal performance --> iPhone Battery and Performance - Apple Support

Batteries degrade with use and over time. Maintaining 100 percent capacity is simply impossible.