Costa del sol
Ingredients: 2 oz light rum, 1 oz sweet vermouth, 1 oz simple syrup, 1/2 oz lemon juice. Pour all ingredients on top of ice and then top with 3 oz soda water.
Source: Cocktail Flow app
This reminded me a bit of a sling. Personally it was way too sweet for me, especially in the winter when I like drinks a bit more tart.