As of Houdini 16.5, the Sketchfab exporter is natively integrated! As long as you have the latest version, you can already export your models directly from Houdini.
How to use
Open your model and apply any textures.
Add the Sketchfab exporter node from the Game Development Tool Shelf.
Enter a title, description, and tags.
Authenticate the exporter using your Sketchfab account email address and password or your API token.
Houdini will export your model with textures, then upload it to your Sketchfab account.
When the upload is complete, you can view your model on Sketchfab, adjust rendering settings, and save the default view.
For more detailed instructions and other information, visit the blog or watch the video above.