Really depends on how you are travelling and where you are going. We recently took 20mo dtds to Canada and knew we could get nappies etc out there so took very few in luggage. If you are going on a plane and need to take fluids you will have to taste a sip of 50% and need a container to transfer into so they don't leak.
Yes, they made me taste the bottle of pre-made formula I was carrying at Gatwick, which meant that by the time we got to our destination it had been open and unchilled (they also made us leave behind our ice block) for ours, so we had to throw it away. Maybe take some emergency powder?