Milk is fabuless for your teeth. Orange juice enriched with calcium is also nothing to scoff at. Really moderate amounts of anything short of crystal meth isn't that bad for your teeth. As long as you're practicing good oral hygene you should be able to periodically have acidic or surgarry beverages and still expect to have functioning teeth well into your twilight years

Anything that has any form of sugar digestable by bacteria is not good for your teeth however anything in moderation and good oral hygiene likely won't cause problems. That being said drinks that don't have sugar would be water, tea, and black coffee(but will stain)

Both milk and orange juice(which is also an acid) have sugar so I would hesitate to say they are good for your teeth.

Both milk an Orange juice contain calcium, which is phenomenally good for your teeth. Orange juice also contains Vitamin C which is essential healthy enamel. Orange juice both citric acid, which could damage your teeth over the course of a decade of constant exposure. I would not advocate you drinking more than 40 gallons of orange juice in a sitting or chemically distilling orange juice to concentrate it's more acidic properties. With good oral hygiene, moderate amounts of acidic or sugary beverages aren't dangerous to the health of your teeth.