A gym equipment rental business can streamline its booking process using a custom scheduling system developed with Java, JavaSpark, and the Nylas API. This system allows users to log in via their Google account, select a time slot, and receive a calendar event and confirmation email for their reservation. It involves setting up a Nylas application and a Google Cloud project, utilizing ngrok for exposing local applications to the internet, and configuring the Java application with Spark and Handlebars templates. The application restricts reservations to one per day and ensures selected slots are marked unavailable. This system exemplifies how to integrate scheduling features into a web application, enhancing user experience and operational efficiency, while utilizing the Nylas Calendar API for calendar and event management.