Bring water and rice to a boil in a saucepan over medium-high heat. Reduce the heat to medium-low, cover, and simmer until rice is tender and liquid has been absorbed, about 20 minutes.

When the rice is almost finished, whisk broth, cornstarch, soy sauce, brown sugar, and garlic powder together in a bowl until thoroughly combined.

Heat a large skillet or wok over medium-high heat. Add beef and cook until browned and juices have evaporated, 3 to 4 minutes. Stir in broccoli and cornstarch mixture; bring to a boil, then cook until mixture thickens.

Serve over hot rice.