Gimballed drink holders exist, chiefly for boating, but you seem to want a gimballed cup that is meant for carrying rather than mounting to something. This kind

Gimballed drink holders exist, chiefly for boating, but you seem to want a gimballed cup that is meant for carrying rather than mounting to something. This kind of falls short of being a gimballed cup but seems neat nonetheless: https://www.3dagogo.com/EricYoung/designs/GimbalDrinkHolder https://www.3dagogo.com/EricYoung/designs/GimbalDrinkHolder