Cooling sportswear products have been used to improve the comfort of individuals exposed to hot–humid climate conditions; however, these products were not explored adequately in the outdoor sports context. Moreover, it is not known if these products meet the needs of athletes in developing and tropical countries. Therefore, this study presents the design and exploratory evaluation of affordable cooling sportswear (T-shirt). Eight Sri Lankan athletes tested the sportswear prototype over three-weeks, undergoing a 30 min cycling trial that covered 15 km. The results show that the cooling sportswear improved cooling comfort, sweat evaporation, and overall comfort of the athletes by increasing ventilation and reducing body temperature. The developed prototype assisted in identifying suggestions for designing cooling sportswear products, including aesthetic, cost, functional, and sustainability considerations. These suggestions may guide researchers to develop affordable and sustainable cooling sportswear for endurance cycling athletes living in developing and tropical countries.