I introduced water along with solid, starting with just a few sips after each feed. Once they're a bit older and can hold their own cup I let them decide how much to drink. As for veggie you can start with potato, pumpkin, sweet potato, spinach. You can puree and mix with rice cereal or porridge. A bit older you can try ones with a bit of texture like carrot, asparagus
Butternut squash is one of the first foods we introduced.