Preheat oven to 350°F. Line a standard muffin tin with 12 cupcake liners. Lightly coat liners with nonstick spray.
In a large bowl, whisk together almond milk, grapefruit juice, oil, sugar, grapefruit zest, and vanilla.
Sift in flour, baking powder, baking soda, and salt. Mix until smooth.
Fill liners two-thirds full. Bake 18 to 22 minutes, or until a toothpick inserted in the center comes out clean.
Cool cupcakes in the pan for 5 minutes, then transfer to a wire rack to cool completely.