A fluid mixing device includes inlet ports in fluid communication with respective source containers, an inlet check valve, a mixing container in fluid communication with the inlet check valve, a discharge port in fluid communication with a target container, and a discharge check valve in fluid communication with the mixing container and the discharge port. Responsive to a negative pressure at the mixing container, fluid is drawn from the respective source containers through the inlet ports and through the inlet check valve and into the mixing container, while the discharge check valve precludes drawing of fluid from the target container. Responsive to a positive pressure at the mixing container, fluid is expelled from the mixing container through the discharge check valve and into the target container, while the inlet check valve precludes discharge of fluid from the mixing container to the inlet ports and the source containers.