Even though there are numerous benefits of drinking alkaline water, I believe the four most important include the following:

Neutralize free radicals.
An abundance of free radicals in the body can cause cellular damage, chronic inflammation, and oxidation (i.e., accelerated aging). Fresh ionized water has a negative oxidation reduction potential (- ORP) which makes it a strong antioxidant that can help neutralize free radicals in the body and excrete toxins.
Alkalize the body.
Most people in our culture tend to be highly acidic, primarily from stress, poor diet, inactivity, and various other factors. According to many experts, acidosis is one of the primary underlying causes of disease. Ionized drinking water has an alkaline pH (ranging from 8.5 pH to 9.5 pH), which helps to balance the body pH in a safe and natural way.
Increase hydration.
Ionized
water is restructured, reducing the size of water molecule clusters while increasing cellular hydration. Increased hydration also improves waste removal from the cells.