Do you explain to her why she can't bathe when she wants or have the juice that she wants?
Kids are smart, if you engage on conversation with them, they will understand and also improve their vocabulary.
The explanation should be before she starts crying, of course, because it is really difficult to get a kid to understand when they are throwing tantrums.
But like Benni said, she is in the Terrible Two's phase, and you need a lot of patience with her right now.
I've worked with kids, and many parents, when their kids were throwing a tantrum over something, would either continuously speak to them in a soothing tone about WHY they couldn't have or do something, or they would just let them crying, to show them that crying doesn't work. Never give in after you have said no, that's how brats are raised.