He definitely needs fluids. If he's got a tummy bug, it might be worth trying Pedialyte from the bottle - that has all the electrolytes that he needs but it isn't EBM, so it might mean he doesn't begin to associate the bottle with EBM

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Is it that you don't want to give him anything that's not directly from the boob, or are you happy to give him stuff as he needs, just not EBM??