Soup up is a colloquial phrase used to describe the act of modifying or enhancing something, typically a vehicle or machine, to make it faster, more powerful, or stylish. Antonyms for soup up include words like simplify, streamline, and downgrade. Simplify implies stripping down something to its bare essentials, reducing its complexity to make it more efficient. Streamline refers to improving something's efficiency by eliminating unnecessary components or processes. Downgrade suggests reducing something's value or performance level intentionally, whether to save money or because it is no longer necessary. Antonyms for soup up can be useful when seeking to simplify or make an object more practical.