Question: How do I refill a foaming hand-soap container with regular liquid soap?
Option 0: You need to fill the container with about 2/3 liquid soap and then add water to the top. Now, it will foam.
Option 1: You need to fill the container with about 1/5 liquid soap and then add water about an inch from the top so it has air. Now, it will foam.
Answer: 1