The boys had two different squirt bottles, but the one that functioned with a hollow drawing tube has lost that tube, and now only squirts if held upside-down. This is too much work, apparently, so they took to just filling the bottles and shaking water at each other. Connor opts for an overhead dump approach, since he's half again as tall as his brother. Griffin shakes three or four lashes at Connor--then throws the bottle at him.
I watch this happen, and it suddenly occurs to me: I'm watching somebody make the same choice that's mystified me in movie context for decades. You know how someone fires a gun until the clip or revolver is empty, then throws the gun at the bad guys? By now, everyone in the theater just groans, if you see it at all anymore; endless ammo or reloads on the fly have been pretty much de rigeur since The Matrix. I've never understood how throwing the gun makes sense, or how anybody could be short-sighted enough to throw away the only weapon they have, in hopes of the possibility of inflicting, at best, a bruise.
Well, apparently, they're thinking like three-year-olds. Mystery solved.