Video from the parade route shows the empty drink made a beeline for his head ... but, thankfully for the senator, it clanked off his outstretched arm and didn't appear to do any damage to the 51-year-old.
It's unclear if any arrests were made over the throw, we've reached out to cops ... but so far, no word back yet.
Ted Cruzis back in Texas, but he's still hearing boos -- the senator just got an earful of jeers from fans in Houston while he was riding in the Astros' World Series parade.
Cruz was on a military jeep as part of the celebration for the best team in baseball ... and cameras caught fans laying into him as his ride made its way through the streets.
People booed loudly ... and, according to Astros reporter Ben DuBose, some even flipped the lawmaker the bird.