Thala-siren milk, often called green milk, was a nutritious milk of a green hue. Female thala-sirens produced this salty liquid for their offspring.
On the planet of Ahch-To, Luke Skywalker consumed this milk after gathering it from the creatures during his chosen exile. It became a key source of sustenance for him. These thala-sirens were very calm and did not object to Skywalker milking them. During the war between the Resistance and the First Order, green milk was shipped to Bubo Wamba Family Farms located on the planet of Batuu. It was then sold to both residents and visiting people at their Milk Stand found in Black Spire Outpost. They also incorporated it into the Green Milk Cooler, an alcoholic drink.
Mark Hamill stated that the substance used on screen was coconut milk, with the color being altered later during post-production. The actual Milk Stand at Star Wars: Galaxy's Edge offers "green milk," which is a frozen, plant-based mixture of rice and coconut milks. The menu describes it as having "zippy citrus and tropical characteristics." The alcoholic Green Milk Cooler is also available at the location in Disney's Hollywood Studios.
The 2020 video game expansion The Sims 4 Star Wars: Journey to Batuu, which is non-canon, features green milk. The player's Sims can purchase it as a beverage from the Milk Stand vendor in the Black Spire Outpost area. Also, it is available as a quick meal from refrigerators in the home neighborhood.