Elixir Soup is an item from The Legend of Zelda: The Wind Waker. A soup made by Link's Grandma, it will fully heal Link's health and magic if he drinks it. Aside from that, however; it will also double his attack strength, making Link's sword glow (this will last until he takes damage). When obtained Elixir Soup is stored inside a bottle, and can be used for two servings.
Link can get Elixir Soup after he cures his Grandmother, when she falls ill. Link does this by capturing a fairy in a bottle and releasing it near her to heal her. After she is healed, Link can return anytime to get a bottle of soup from her.