tl;dr: It's doubtful that this would classify as assault in most cases. That said, there is a chance it might result in an assault conviction depending on how it happens. I'll focus on these more unusual cases below.
Background
New York is a little different than a number of other jurisdictions in the united-states. What would typically be called battery is called "assult" in New York, and what would usually be called assault is called "menacing."
N.Y. classifies assault in three degrees. First degree assault is the most serious, but what we're after is third degree assault.
It is governed by N.Y. Pen. Law § 120.00:
A person is guilty of assault in the third degree when:
- With intent to cause physical injury to another person, he causes such injury to such person or to a third person; or
- He recklessly causes physical injury to another person; or
- With criminal negligence, he causes physical injury to another person by means of a deadly weapon or a dangerous instrument.
Assault in the third degree is a class A misdemeanor.
This is different from the common law elements of battery which are often summarized as an intentional, offensive, unprivileged contact. In particular, N.Y. allows three avenues to assault.
Most of the time squirting water from your run-of-the-mill water bottle isn't going to trigger any of these. However there are situations in which you might trigger the second avenue
- It's not hard to make a case that squirting a driver or bicyclist--so as to imperil the operation of the vehicle or bike--would qualify as reckless behavior, where recklessness is a significant deviation from what a law abiding citizen would do. If the driver or bicyclist is injured as a result, it likely satisfies the elements for 3d degree assault
- But I wouldn't confine this to people operating modes of transportation. Imagine a squirting a pedestrian who slips and falls; imagine someone's eye being injured; imagine someone walking into a pole
- Likewise, criminal negligence is an even lower standard than recklessness (i.e. it's easier to show something was negligent than that it's reckless). The tradeoff is that you'd need to consider the water bottle a dangerous instrument. That's a stretch, but if there were an injury you'd certainly have a creative attorney trying to make it fit