The phrase "used sparingly" implies the careful use of something to avoid waste or overuse. Some words that can be used as synonyms for "used sparingly" include "economical," "moderate," "infrequent," "scanty," "limited," "restrained," "frugal," "measured," "occasional," "sparse," "minimal," "restricted," "conservative," "careful," "judicious," "prudent" and "selective." When used in writing, these synonyms can add variety and depth to the language, conveying a more nuanced meaning to the reader and creating a more interesting and engaging reading experience. These words can be especially useful when writing about sustainable practices, effective resource management or any topic where the careful use of resources is critical.