Is there a way to make tapered lines in Sketch? I attached the way I do it in Illustrator as an example below.
I don't use Sketch, but it does have a Vector Tool for making Bezier curves somewhat similar to the Pen Tool in Illustrator.
To make a tapering line in Illustrator without using a stroke style/profile it's easy enough to make by simply using the Pen Tool, so the same should be possible in Sketch and virtually any vector image editor with a similar tool.
Remember to set the stroke to none, and the fill to black.
There's a tutorial on youtube showing how to use the Vector Tool in Sketch here