Wash or rinse the grapes in running water to remove dirt and Remove stems.
Place cleaned grapes in a blender jar.

Add 1-cup water and blend in the blender until smooth.
Place a large fine sieve (a strainer) over a large bowl and pour prepared juice over it. Press the pulp gently using a spatula to get the maximum juice out of it. Discard the solid pulp. You can also use muslin cloth or nut-milk bag to strain the juice.

Squeeze the lemon over it and add ice cubes. Stir with a spoon and taste the juice, if it is too sweet, add 1/2 cup more water or as needed according to the sweetness of grapes and stir. Pour prepared homemade grape juice into serving glasses and serve.