My child refused to take a bottle so I had her use a sippy cup from about 5 months (she breastfed for a year but by then was down to one feed a day). The health visitor said there’s no reason not to. I would have to hold it initially and obviously it can pour out so you have to be careful. A little bit at a time and she got used to it and when she could pick it up and hold it by herself hurrah! It was just water I wouldn’t put anything like juice until a year or so and then really watered down.