The pace in group rides and races usually varies. When there's a lull in the action, take a drink, even if you don't need it yet. If you wait till you need a drink then the pace may be too fast to take one.
You may be holding your breath while you fish for the bottle. On your solo rides practice grabbing and putting the bottle back while not interrupting your breathing or pedalling or looking down. Once you have that down you will only have to stop breathing for as long as it takes to swallow.