Use chef’s knife to cut steak with grain into 3 or 4 strips (each about 2 inches wide).
Cut each strip across grain into thin slices, about ¼ inch thick.
In medium bowl, whisk 1 tablespoon water, soy sauce, cornstarch, and baking soda until combined.
Add sliced beef to bowl with soy sauce mixture. Wash your hands. Use rubber spatula to stir to coat. Let beef sit for 15 minutes.
While beef sits, in second medium bowl, whisk hoisin sauce, chili-garlic sauce, and remaining ¼ cup water until combined.
When beef is ready, heat oil in 12-inch nonstick skillet over medium-high heat for 1 minute. Use rubber spatula to carefully add beef to skillet and spread it into even layer. Cook, stirring occasionally, until beef is lightly browned on both sides, 2 to 4 minutes. Turn off heat and use rubber spatula to transfer beef to large plate.
Add hoisin mixture, broccoli, and garlic to skillet and return to medium high-heat. Cook, stirring occasionally, until sauce is thickened and broccoli is tender, about 5 minutes.
Stir beef and juices on plate back into skillet and cook for 1 minute. Turn off heat. Serve.
