I can't imagine that buying a juicer and fresh veggies would be more expensive than a lifetime of buying premade and prebottled stuff. I know you say it would save you the cost of the veggies, but veggies, especially the green ones, aren't that expensive. And it'll be way healthier and fresher if you make it yourself. You could probably make a batch once or twice a week and put it in old water bottles.
Probably would look really gross though. Maybe some opaque water bottles?