There's always room for discussion, but perhaps the sections Drinking Water and Beer from our FAQ located in the sidebar will answer your inquiry.

Medical student and amateur historian. I may be some help.

Yes, it was common practice in many societies throughout history to drink alcohol instead of water. The bible even argues against drinking water.

The alcohol drank would have had a low alcohol content. This would have helped to increase safety without much of the dehydrating effects.

Recent studies have shown that beer with a low alcohol percentage such as light beer can help to replace fluids and electrolytes lost during physical activity.

Source Articles:

Alcohol in the western world: A history. Published Scientific American. 1998

Beer as a sports drink? Manipulating beer's ingredients to replace lost fluid