I’m not a dietitian, but I would assume either one of these would be a very bad idea. Energy drinks can have a lot of sugar in them and not much else, so I don’t see how you could get any of the nutrients you would need to survive.
I would guess milk has a lot more things in it – such as fats, minerals and vitamins, and proteins (yay!), but still I don’t think you survive very long if you drank only milk.
Neither energy drink or milk have all the vitamins and nutrients you need in as Sam said.
Energy drink alone aould make you feel very ill as it is mostly just sugar and you wouldnt be getting things like vitamin C and could end up with Scurvy which is a vitamin C deficincy which lots of sailors used to get bucause they didnt eat fresh fruit and vegetables which contain lots of it.
As Sam said milk has more good things in it like fats and calcium but I dont think that just drinking milk would have enough in it to make you feel great either.
I wouldn’t say either of them would be all that healthy and you’d probably get sick from either of them. But, if I had to say either- I guess milk might be the better option- it’s more natural, has lots of calcium and has some healthy fats in it. On the other hand, energy drinks are full of sugar (unless you buy sugar free, of course!) and caffeine and wouldn’t be all that good for you at all!
As the others said, for a healthy human, you need the right nutrients. Therefore missing out your fruit and veg would be a problem and you would get sick. Neither milk nor energy drinks have enough nutrients to survive.