As someone who used to do this. OpenAI models refuse to look up calories unless you explicitly tell them to and even then it is a hit and miss even if you tell them exactly what the product is. Easiest way to get good calculation is to just take a photo of the nutrition label or feed that info in by hand.

Funny thing is 4o did look up calories but I guess it was too good for this world

I exclusively use thinking mode, which is slower but much more likely to double-check things with web search etc.