I do this personally. I drink water with every meal. I can't tell you how many pounds I've kept off my body due to this. Actually, yeah I can. Drinking water instead of juices or soda makes a 10-20 pound difference (and that's just from 1 juice or soda daily).
Juices are often high in sugar or chemical sweeteners. Diet drinks are questionable from a health standpoint. Give your body the water it craves and it will reward you with better health – all the way down to the cellular level.
An added plus: drinking plenty of water helps keep you from consuming excess calories, too. If you're hungry, drink 8-16 ounces of water first. Then eat.