We've used a variety of hydration packs and vests over the years and USWE is our favorite. This vest is a great option because it holds 2 liters of water, has front pockets for food, phone, etc. and has a stretchy back pocket for bigger items like tools, a tube and a jacket. If also keeps your jersey pockets accessible. See below for how we attach our GoPros.
The rest of this recommendation is only available to paid members.