I found this recipe on liquor.com.

gin, cherry liqueur, herbal liqueur (I used Campari), Cointreau, pineapple juice, lime juice, grenadine, bitters, club soda⁣
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Finally! I’ve been wanting to try this cocktail for a long time. Even though I didn’t know anything about mixed drinks before I started this project, somehow I’ve known the name “Singapore Sling” since I was a kid. For whatever reason, I was a kid who thought walking into a bar and ordering a Singapore Sling was the height of sophistication. I must have seen it in a movie or something.⁣
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But it’s taken me a while to get to this cocktail in The Drinky-Drink Project, mainly because it took me this long to accumulate all of the ingredients. ⁣
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The Singapore Sling was created at Raffles Hotel sometime before 1915 in Singapore. It was created to get women drinking…the idea that it looks more like fruit juice than drinking a glass of gin. The original recipe is lost to time, so recipes for this are all over the place. My research tells me that the recipe I’m using is believed to be closest to the original.⁣
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It was worth the wait! This tastes like a fruit punch, and I think it’s the most delicious fruit punch I’ve ever had. Mainly because there are more complex notes going on with the Campari and bitters, so it’s more than just fruity. The only sweetness is from the pineapple juice (and I suppose the Cointreau, too, but there is very little in there), so it’s sweet, but not like candy. It’s so good.⁣