You can measure how much water you have in a cup. But the water has no specific shape. You can pour a cup of water into a bowl and it takes the shape of the bowl. But it still has a volume of 1 cup. Definite volume, no definite shape.
Milk is a liquid.
Soda is a liquid. Matter that has no definite shape and no definite volume is a gas . For example, air has no definite volume and will change shape according to the things around it. Air is a gas. Oxygen is a gas.