"Sowing one's oats" is a common idiom that refers to a period of time in a person's life when they engage in frivolous activities, especially sexual encounters. However, there are several other synonyms that one can use instead of this phrase. "Exploring one's sexuality," "living it up," or "dabbling in experimentation," all convey the same idea as "sowing one's oats," but with less of a derogatory connotation. "Having fun," "being adventurous," or "enjoying life" are also suitable alternatives. In essence, any phrase that represents a youthful phase of experimentation and self-discovery could work as an alternative to "sowing one's oats".