Step 1

Bring water, rice, sugar (if using), oil, vanilla (if using), and salt to simmer in large saucepan. Cover and simmer over low heat until rice is very tender, about 12 minutes.

Step 2

Carefully transfer rice mixture to blender and process until opaque and smooth, about 1 minute. Strain blended rice mixture through fine-mesh strainer into 4-cup liquid measuring cup or large bowl, stirring to extract as much liquid as possible; discard solids. Let cool to room temperature, about 30 minutes. Transfer milk to airtight container and refrigerate until well chilled, about 1 hour. Serve. (Rice milk can be refrigerated for up to 4 days; stir to recombine before serving.)