sweet has 27 distinct synonyms spread across 13 of its 16 senses. Each sense below keeps its own list, because a synonym belongs to a meaning and not to a word: swapping one sense's substitute into another sense's sentence is how a thesaurus makes writing worse. Its 2 recorded opposites are sour, dry.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
having or denoting the characteristic taste of sugar
having a natural fragrance
“odoriferous spices”
(used of wines) having a high residual sugar content
“sweet dessert wines”
with sweetening added
English phonetician; one of the founders of modern phonetics (1845-1912)
a dish served as the last course of a meal
a food rich in sugar
the taste experience when sugar dissolves in the mouth
the property of tasting as if it contains sugar
in an affectionate or loving manner (`sweet' is sometimes a poetic or informal variant of `sweetly')
“Susan Hayward plays the wife sharply and sweetly”
1 of the 16 recorded senses carries no synonym, antonym or related term, so it is not shown above. Every sense, with its definition and examples, is on the full entry for sweet.
Synonyms, antonyms and the broader and narrower relations for sweet come from Princeton University’s WordNet. Full sources and licences.