The growing consumer focus on well-being and sustainability, coupled with the widespread adoption of plant-based diets, has fueled a significant surge in the global functional drink market, which is expected to expand by USD 13.7 billion from 2024 to 2028. These types of beverages have emerged as a leading segment due to their ease of use, sensorial desirability, and capacity to vehicle bioactive compounds in relevant physiological concentrations. Today, R&D lines are being focused on formulations fortified with antioxidants, vitamins, essential amino acids, omega-3 fatty acids, prebiotics, and probiotics, with synergistic benefits in the modulation of the immune system, inflammation, or cognitive health. Quantification of these compounds is a critical stage in the design, control of quality, and compliance of functional drinks. Yet, their screening involves technical hurdles given the complexity and variability of food matrices, ranging from simple aqueous mixtures to colloidal systems or stabilized emulsions, as in the case of dairy-type beverages of vegetable origin. Moreover, it is often required to simultaneously detect multiple analytes with diverse physicochemical properties, which increases analytical difficulty. Against this backdrop, biosensors are emerging as encouraging analytical platforms that deliver high sensitivity and specificity, real-time response, and miniaturization potential for in situ solutions. In particularly, electrochemical and optical biosensors have proven to be effective in targeting key bioactive compounds in complex matrices. The latest progress in transducers based on nanotechnology and biological recognition elements like aptamers has significantly improved detection limits and operational stability. Therefore, this systematic review, conducted in accordance with PRISMA guidelines, will give an up-to-date overview of the state of the art in biosensing technologies applied to functional drinks by critically performing parameters and long-term potential for more scalable, intelligent, and affordable food analysis systems.