I'm with KimmyT. I'd be concerned that the tubing would get caught on something and send me sprawling. I think if you just kept practicing you'd get it. Also, it will make you a better bike handler to be able to get your water bottle. Compensating isn't always better than learning a new skill...especially if that new skill will help you in the long run.

Maybe you could start out by just reaching down with your hand and resting it on your knee. Just coast and/or pedal for awhile like that. Then move your hand back up to the bar. Repeat. Then after you've got that down move your hand down to your shin...then move down and actually touch the water bottle but don't remove it...just keep your hand on it for awhile. Maybe that would help???