At the age of 6 months, your baby can sip water from a cup or you can mix water with his cereal to make it thinner.
Try to avoid bottles full of water as they tend to give the baby a false feeling of fullness and he might not eat well.
If you are on city water, you don't need any additional flouride drops. If you are on well water, this is a good time to talk with your pediatrician about a fluoride supplement.
I hope this helps!
Let me know if you still have questions.