Happy Things for After You've Seen GoT S6E5 by PahuskiM

Question 10

If you're looking to enjoy a tropical happy hour, you might try a cocktail invented by Ngiam Tong Boon around 1915 in the British Straits Settlements. The original recipe called for orange, lime, and pineapple juices, cherry brandy, and one other spirit. What missing ingredient helps a Singapore Sling do its thing?