Saccharin, with no e, refers to a white crystal powder used as a calorie-free sweetener. It is always a noun. Saccharine, meaning (1) sweet, (2) cloyingly sweet, or (3) excessively sentimental, is always an adjective. The words are pronounced alike, but that e is pivotal in writing.
He offered the example of saccharin, a sweetener often used in coffee that until recently also appeared on the federal list of substances regarded as toxic waste. [NY Times]
EPA removed saccharin from the list recently, a decade after the science supporting the move came together. [Huffington Post]
Given as if in an arrangement by Cécile Chaminade, mushy and saccharine-sweet, this accompaniment undermines every stylish moment of the dance. [Financial Times]
Adults, unless horse-racing fanatics, will find it cliché-ridden and uncomfortably saccharine. [Inside Pulse]