Text on Path
Sketch supports can render text on path, such as the example below:
There are two things we need for this to work; a vector shape and a text layer. When you go to the Type menu and enable Text on Path, Sketch will put the text layer on the line of the vector shape underneath it. Note that it only works if the vector shape is below the text layer; the order of the layers has to be such that the text layer sits on top of the vector shape.
Placing the text layer on the vector is as easy as dragging it horizontally across the shape. It may be hard to describe in writing, but you will see that it works very intuitively.