Objective: Transitioning from a bottle to open cup drinking can be a lengthy process in typical development. Children are often introduced to training cups during this period. Due to a lack of standardization in commercially available training cups, differences in design and performance characteristics may potentially create medical complications in developmentally delayed individuals. Our purpose is to report commercially available training cup design characteristics, residual fluid, flow rates, and suction pressures and discuss the potential clinical implications. Design: A testing apparatus was developed to determine suction pressure and flow rate. Nine commercially available training cups were tested by two independent research teams. Experimental data were filtered and then fit with a linear approximation determined by a least squares method. Results: Commercially available cups exhibited extensive variability in design parameters, suction pressure, rate of flow, and residual fluid. Conclusion: The extensive variability of design and function within current commercially available cups has clinical implications for children with development delays such as the ingestion of air and aspiration. Studying the variability of existing training cup performance identifies characteristics that impact cup function which can influence future cup design.