Arrow of spraying

This arrow when fired turn into a spray of water mid flight.
Not sure what spells or level needed to create this item or uses of same, help!

To me this seems like a charged item enchanted with a CrAq effect.

What is the intended purpose of the item? Do you want, perhaps, to spray a crop? If so, remember that magic won't be a good option (because the water will disapear unless a ritual is used, and you can't invest a ritual into an item w/o a virtue or a breakthrough).

Mostly it’s to help destroy vampires.

A Mutantes Mercere can transfer a spell in an arrow and have this effect without the need for enchanting

You mean, by spraying holy water upon them?

The two ways I'd look at it: You could have the arrow transform with MuHe(Aq), duration only needs to be momentary if the liquid impact is the important part. The other option is having the water turned into an arrow, but that's more tricky, mechanically.

If your intention is just to create a jet of water to hurt or push someone, it's not that hard. The arrow becoming water is just cosmetic, the actual effect is Creo. You will need additional levels for penetration for it to be useful against targets with MR.

Arrow of Water
CrAq 15

This arrow becomes a torrent of water mid flight. Since it just needs to be shot at the direction of the target, the arrow cannot be parried or blocked, only dodged, but it still needs to hit. The target takes +10 damage instead of the regular damage, and must make a Strength + Size stress roll of 9+ or be sent flying back. Afterwards the arrow reverts back to it's original form.

(Base 10, +1 Touch)

Note that the arrow itself becoming water and changing back is just cosmetic, the spell effectivelly creates a jet of water.

To spray holy water I think you could use a ReAq effect.

Arrow that Brings the Blessed Spring
ReAq 40

This arrow must be crafted with an arcane connection to a container of holy water within 1 league. Upon being shot it transports 16 ounces of water from the container, spraying it along it's flight path.

(Base 15 (transport a liquid instantly up to 1 league), +1 Part, +4 AC)

This assumes that you can target the water with an AC to it's container, which might not suit everybody's tastes. Part is necessary because you don't want/need to transport all the water in the container (and if the container is too large it might even be impossible without additional magnitudes for size).

The actual effect of sprinkling someone, or something, with holy water, is better left for the storyguide to adjudicate.

Both items I proposed above would be charged items.