If LN would allow payments without first sending a payment request (I'm hoping future versions will allow this)
A hack for this which has been possible since the beginning is using circular payments.
The
sendinvoiceless C-lightning plugin by Galizoltan allows this.
Otherwise there is keysend, as mentioned above.
But I wonder why everyone keeps calling this Sphinx.This is Sphinx (to me).I also understand Sphinx to have zero relationship with invoiceless lightning payments, although I've not heard anyone saying it does up until now