One instance of a cat drinking 4oz of water in a sitting is not really alarming, but if you are noticing a pattern of your cat drinking more water than usual, repeatedly emptying the bowl in one sitting, or other unusual patterns of excessive water drinking, that is a reason to take your cat to the vet. It can indicate diabetes or kidney disease, or a number of other conditions, most of which are well treatable if caught early, and much less so if ignored until they are showing more severe symptoms.
It's possible that the extra sweets made her extra thirsty, but I am inclined to think that the drinking after eating a sweet is likely a coincidence.