The antonyms for the word "sweatiest" are numerous, but all of them have one thing in common: they describe a state of dryness. For example, "driest" is a perfect antonym because it suggests a lack of moisture, as does "arid", "parched," or "dry." Other antonyms for "sweatiest" include "cold," "chilly," "cool," and "frigid," all of which suggest a lack of heat or warmth. Finally, if you want to describe a state of cleanliness, you might use "cleanest," "purest," or "spotless" in opposition to "sweatiest.