I've tried that before with my 18" AK.
I also found that I'm way better coming from my left side; it always hits and twists coming from the right. It's also really cool when you hit it perfectly. (Keep in mind that the spine on my AK is a half-inch thick, too.) It's like the bottle just jumps out of the way. All you hear is "swish" as you cut the water. ^o^
I cut some bottles so cleanly that the flimsy plastic label wasn't even torn, and you could just set it back together... now that was cool. On the other hand, I've botched some swings by hitting too close to the tip of the blade, and at an angle; The AK just twisted (taking my wrist along for the ride,) and sent the bottle 20 feet off to the side, spurting water.
Also, when I was doing this, it was about -20C outside, so I filled the bottles with hot water from the tap. It makes a cool effect when you slash open a bottle, and it lets off a cloud of steam... it also tends to freeze you much less if you get sprayed. (I did an underhand slash, and got soaked. Luckily, I was wearing a trenchcoat, so I stayed mostly dry underneath.)