In a large saucepan, bring 3 cups (720ml) water to a simmer. Whisk in sodium citrate until fully dissolved. While maintaining a gentle simmer, add cheddar cheese in small increments, using an immersion blender to incorporate it completely into the sauce before the next addition. When all the cheese is added and the sauce is smooth and glossy, blend in hot sauce, mustard powder, and garlic powder. Season with salt, if necessary.