The funny thing is as long as you have a small kid with you - doesn’t even have to be a baby, just stroller-age - you can bring anything. I’m not even talking about a sealed bottle of water - which, to me, would kind of make sense with the regulations - but all of the sudden your normal 500ml bottle with water, juice, or whatever, is fine. A thermo can with boiling hot water inside? Sure, no problem.