By the way, not everyone knows that you can wash your head with shower gel. Can you wash your body with shampoo? Not really. Shampoos have antifungal added to them, and they often have a more aggressive composition. Not to mention that shampoo is more expensive than shower gel.

Another discovery. You can brush your teeth with soap. Not any soap, but the simplest soap. Something like Marseille soap (but not Soviet laundry soap). It's not a particularly pleasant practice, but it's better than nothing (if you don't have toothpaste).