Taking vitamins is not going to break your fast but you may want to save them for your eating window to avoid stomach ache and to maximize the vitamin absorption. Many vitamins are fat soluble so if you take it while fasting, you are just going to pee them out.
I can take vitamins on an empty stomach, but not iron. So, ymmv, but heads up.
Personally, I don’t consider them fast breakers on long fasts. I pair with food in eating windows.
For longer fluid and electrolyte only fasts, I use vitamin/electrolyte tablets with minimal calories.
The more I research, the more I’m seeing that the body is pretty self sufficient and the process of fasting helps to repair such mechanisms for the body to get back to homeostasis and not necessarily need such supplements; as most of which are synthesized and not true source.