I set up my phone so I can say "hey Siri ok google" and then it asks me what I want to tell google. I then say any command supported by the Google Assistant, and it passes the command through.
Technically I think it's supposed to work all in one utterance, but I have found that it never works that way. I always have to split it up. Even still, this is a pretty handy way to be able to ask for information (Siri's knowledge seems quite limited compared to Alexa/Google) without having any always-listening devices in my home.