With E10 gas in most of the U.S., there isn't much of an issue with "water in the tank". Yes, there is some water there. It came in with the alcohol, and will go out with the alcohol. You could add a liter or two of water with every tank fill and not have a problem.
If your car isn't 'classic', it probably has a plastic fuel tank and a giant, very effective fuel filter. If it's not an antique, it probably has a well-sealed fuel system with vapor capture that minimizes moisture entry.
There are potential issues with injector deposits, and additives that address the problem. But that would not be listed as a 'fuel system flush'.