IPA: /ˌoʊvərˈswiːtənd/
KK: /oʊvərˈswiːtənd/
Having too much sweetness, often to the point of being unpleasant.
The cake was oversweetened, making it hard to enjoy the flavors.
Oversweetened → It is formed from "over-" (meaning excessively) and "sweet" (from Old English "swete", meaning having a pleasant taste) and "-ened" (a suffix indicating a change of state). The word "oversweetened" means made excessively sweet in taste.
Think of something being made 'excessively' ('over-') 'pleasant in taste' ('sweet') — that's why oversweetened means too sweet.
No commonly confused words.