if you drank only water and maybe some vegetables would you never get acne?!

acne is mostly related to stress and hormone changes

I believe it would be greatly reduced but your hormones and stress level wouldn't be so affected really. You couldn't survive on a diet like that anyway. Best thing would be to examine what you are eating and drinking and try to eliminate unecessary sugars from your diet; sodas, sweets, etc. Also reduce unecessary fats like ice cream (used to be my #1 enemy), cream etc. Try to focus on fresh fruits and vegetables, but avoid dried fruits (high sugar content) and nuts. Try to include lots of green leafy vegetables in your diet; this is what is mostly missed in today's diets. When was the last time you ate cabbage, etc.? I recall my mother saying her friend (in her youth) had to drink cabbage water what the cabbage was boiled in) daily, and that her skin was the clearest and nicest she has ever seen. Doesn't sound very nice but it sounds like the way to go. Perhaps you could include some stock and other vegetables with this and see if it tastes nicer that way.

it depends if you have it badly. For instance, i really dont break out dramatically. But in order to keep my face acne clear i stay away from sodas and candy, especially chocolate. Drinking water will help and you can also have juice. im not sure about the vegetables. I hardly eat veggies, but because i stay away from candy and sodas, my face is clear. i hope i answered your question well enough.

That could possibly work but is it worth it? There are some other ways to avoid acne by still being able to eat. You can eat less oily food and soy milk instead of regular milk. Take a look at this link:
http://www.wikihow.com/Avoid-Acne