There are stomach virusus, but what many people commonly call “stomach flu” isn’t flu at all. "Flu" is short for influenza, and that is respiratory so it involves lungs, not the stomach. What people call a stomach flu is instead viral gastroenteritis. It could be rotavirus, norovirus, adenovirus or something else, and could have been through tainted food.
In a Mayo Clinic video, internist Cindy A. Kermott, M.D. explains the difference and offers advice for dealing with a stomach bug. It is mostly what will need to happen with an actual flu too; a lot of fluids, water or clear soda, maybe some crackers or Jell-o or toast, and rest. Avoid Chipotle.
It mostly just takes time to work its way out of your system. Don't be duped into buying homeopathic nonsense like Zicam either way.
Also worth knowing; if you think you have the flu, you don't have the flu. When you have the dry cough, the fevers, the myalgias, and feel like you've been run over by a New York City bus while a hobo steals your shoes, that is when you will know you have the flu.