It comes with it. I think it's "Alexis".... but I don't use my Firestick so I'm not sure. You will NOT have Siri unless you have an Apple product... like AppleTV, or a HomePod.
Alexis, Siri, same thing.
If you buy an Alexis device to go with the Firestick you can set it up in the room with your TV and simply use voice commands... you don't even have to have the handheld remote.
We need someone who is set up with Google... Alexis... Firestick (all the same), to help out in this thread because they could answer a lot better than I can. As I mentioned... I'm on an Apple system and you certainly do NOT want to convert to Apple just for Sunday Ticket... unless you have a few grand sitting around that you want to spend.