Try asking your Pediatrician.
"Water" is also in his Formula. A baby does not have to drink a whole lot of extra water. He is getting hydrated already with his Formula... and Formula has vitamins/nutrients in it already.
About "juice." Juice is really not necessary. For us, we did not give juice to our kids until about 2 years old. They got kid/baby vitamins anyway, per our Pediatrician. And we only offered juice about 1-2 times a day, at most. And only about 6 ounces.
And even our Pediatrician said there is NO rush, for giving juice. Juice is like drinking a dessert.
Juice is just sugar. It is not real necessary. He is getting fortified with his Formula.
IF you do give juice though... it is always best to DILUTE it with water... 50-50 ratio. My kids are older now... but we still dilute their juice, always. But drinking "juice" is not a habit with my kids. Or, we only buy 100% natural fruit juice. Not with all that added "fructose" or corn-syrup in it. Or we squeeze our own.
If your son does not "like" juice, for now, that is fine. A child does not "have to" drink juice. And for water... I would not add sugar to it just to get a child to drink it... although some might do that.
For sippy-cups.. try different kinds with different spouts. Some spouts are hard or soft. OR... try just getting a straw-cup for him... some kids/babies will drink from that versus a sippy-cup. Or try a regular cup. He may drink from that.
Is he able to "hold" his own bottle, when he drinks his Formula? If so, then he can hold a cup. But perhaps, he is not yet ready for that.
But try asking your Pediatrician.
All the best,
Susan