For how long does sangria last?

Presuming that you're speaking about a sangria that has been made with fresh fruit, and not a shelf-stable item, it will last for about 3-4 days in the fridge. After that, the fruit will start to break down and the sangria will end up being less flavorful. You can freeze the fruit before adding it to the red wine if you're looking to extend the life of your sangria.  https://geogenes.org/?p=653 This will help to keep the fruit fresh and the sangria flavorful for a longer amount of time.