Using Sketch-> Project to text.
Additionally, these 2 methods are both from DesignSpark user- Jacant:
There are two solutions-
Use the 'Dimension' tool to measure an edge. Move the measurement over the face you want the text. Double click the measurement and change the text to suit. Use the 'Project' tool on the new text. Hide the Annotation plane. Pull the text that is now on the surface.