Gainful offers personalized nutrition through tailored protein powders and hydration products for fitness enthusiasts and health-conscious individuals. Customers take a quiz to determine their specific nutritional needs, and Gainful creates a unique protein blend based on the results. The company operates on a subscription model, ensuring regular delivery of products while emphasizing quality and safety with clean ingredients. Gainful differentiates itself by providing customization options, such as flavor boosts, to enhance the customer experience.