Acidic whey, a nutrient-rich by-product of cheese production, is naturally high in quality proteins, lactose, vitamins, and minerals, making it a valuable ingredient for human consumption. Despite its nutritional potential, acidic whey poses a significant environmental challenge due to its high volume and limited industrial utilization. This study aimed to valorize acidic whey by incorporating it into a strawberry-based functional beverage, thereby enhancing its nutritional value while contributing to dairy waste management. The beverage, formulated with 70% strawberry juice and 30% acidic whey, was subjected to different preservation treatments and evaluated over 28 days for physicochemical properties, antioxidant capacity, and microbial stability. Four sample groups were studied: an untreated control (T₀), thermal treatment at 80°C for 10 minutes (T₁), and ultrasonication at 25 kHz for 5 minutes (T₂) and 10 minutes (T₃). Among these, the ultrasonicated sample treated for 10 minutes (T₃) demonstrated the most favorable results, with minimal pH decline and a 42.88% reduction in sedimentation compared to the control (T₀). T₃ also retained the highest levels of total phenolics (725.08 µg GAE/g) and flavonoids (384.85 µg CE/g) and exhibited a 45.71% increase in antioxidant activity. Microbial analysis for T₃ indicated a 74.10% reduction in total plate count.

These findings highlight the potential of ultrasonication (T₃) in preserving the nutritional and functional attributes of strawberry–acidic whey beverages, particularly in terms of antioxidant activity and bioactive compound retention. The study further supports the application of non-thermal processing techniques for developing shelf-stable and nutritious beverages. This approach aligns with sustainable food processing goals by promoting the circular utilization of dairy by-products in value-added functional products. A detailed study on sensory evaluation and consumer acceptability will be conducted in the future following formal ethical approval.