juice in place of fruit

Can I use juice in place of fruit and veggie juice in place of veggies sometimes. Also can I mix the protien shake with skim milk.

If you don't exaggerate, yes, but use 100 % fruits or vegetables and mix them in a blender.
If you use premade fruit juice in bottles you might risk that you get very hungry. The satiation effect of fruit juices is not as high as if you eat the whole fruit.

All the best,

Gabriela