Hi Lyra

It is tricky! My sis visited from the UK last year with a 4month old. She had the ready made formula and didn't have to taste it. I'm pretty sure she found it available for sale in transit lounge shops too.

BUT noting that different stopover / refuel cities have different rules when you get back on. eg Bangkok is really strict and annoying, they will take the water / coffee you just purchased in the transit lounge!! In contrast singapore is more reasonable.

I suggest you call your airline and ask to speak to someone who can give you reliable advice. Ask them about availability of water on board, taking on empty bottles, and how to bring premade formula on. They might suggest who else to consult with too.

I don't envy you, I know my sis was very stressed before hand but eventually got reliable advice and all went well. Good luck!