Quoting from Wonderbook: Book of Spells:
The Water-Making Spell conjures clean, drinkable water from the end of the wand. Thus, with the Water-Making Spell the trained wizard is never without a source of water, whether they’re refilling their goblet at dinner, or managing a minor eyebrow fire after a carelessly-cast Fire-Making Spell.
However, we know that food is the first of the five Principal Exceptions to Gamp’s Law of Elemental Transfiguration.
"Your mother can’t produce food out of thin air," said Hermione. "No one can. Food is the first of the five Principal Exceptions to Gamp’s Law of Elemental Transfigur—"
"Oh, speak English, can’t you?" Ron said, prising a fishbone out from between his teeth.
"It’s impossible to make good food out of nothing! You can Summon it if you know where it is, you can transform it, you can increase the quantity if you’ve already got some —"
(Harry Potter and the Deathly Hallows, chapter 15)