There are a few different ways that you can measure 5/8 of a cup. The most common way is to use a measuring cup that has markings for various measurements (including 5/8 of a cup). If you don't have a measuring cup, you can also use a regular drinking glass or mug as long as it has markings on the side for fluid ounces. To measure 5/8 of a cup using either of these methods, simply fill the container up to the 5/8 mark and then pour the liquid into your desired vessel.
Another way to measure 5/8 of a cup is by using standard kitchen utensils. For example, 1/2 tablespoon is equivalent to 1 fluid ounce, so if you need 5/8 of a cup, you would use 10 tablespoons + 2 teaspoons (or 30 teaspoons). 1 tablespoon is also equal to 3 teaspoons, so another way to do this calculation would be 6 tablespoons + 1 teaspoon (or 18 teaspoons).