My wife, son, and me went through the metal detector (shoes off and all of that), put all our stuff on the rollers for the x-ray machine, and went over to pick up our stuff.
While picking up our belongins, a male TSA agent took my son’s sippy cup and went over to a machine towards the end of the security section. It was some kind of “sniffer” and they asked me what was in the cup. I told him milk and they put it in the machine to make sure it was milk. Then he gave us back the cup and we left security.
That pretty standard procedure for bringing liquids through security. thanx