The little girl accidentally drinks a bit of her mother's Screwdriver (orange juice and vodka,) and then supposedly gets tipsy and is able to see the ghost. Even if she had drank the whole glass, there is not nearly enough alcohol in there to have any sort of effect on her, let alone to that degree, and certainly not within moments after drinking.
When the ghost launches Garth out of the window at the brewery, the safety mat flops up after he lands on it.