Looks like it's using mm-wave radar technology to detect changes of the dielectric properties of solutions with different levels of glucose.

There is also a paper from them doing it with the Google's Project Sali dev kit, the radar that was mostly demonstrated with gesture recognition, but looks like it's useful for other things too like this. They also show it can be also used to detect glucose levels in drinks too like Coke vs diet Coke.

Besides the current one posted, they have multiple other publications about the topic:

Using Project Sali back in 2018: https://scholar.google.ca/citations?view_op=view_citation&hl...

This one is also nice detailed one: https://www.mdpi.com/2072-4292/12/3/385

and looks like the current one is about improving this technology with enhanced signal-to-noise ratio.