Typically you can not juice using a blender as the mechanism for juicing is entirely different and blenders are not made to extract juice from pulp. You can, however, use a blender to turn softer fruits, vegetables and greens into thicker drinks or smoothies. It's best to use watery fruit and vegetables for this purpose, like cucumbers, tomatoes, celery, apples, pears and watermelon, along with easy-to-chop veggies like spinach.