sauce / source are similar-sounding terms with different meanings (referred to as homophones). To better understand the differences, see below for definitions, pronunciation guides, and example sentences using each term. 👇
sauce: (noun) flavorful relish or dressing or topping served as an accompaniment to food. (verb) behave saucily or impudently towards. (verb) dress (food) with a relish. (verb) add zest or flavor to, make more interesting.
source: (noun) a document (or organization) from which information is obtained. (noun) anything that provides inspiration for later work. (noun) a facility where something is available. (noun) (technology) a process by which energy or a substance enters a system. (verb) get (a product) from another country or business. (verb) specify the origin of.
sauce: s·AO·s
source: s·AO·r·s
(Examples are Wikipedia snippets under the CC ShareAlike 3.0 license. Definitions drawn from WordNet.)