A "thirsty soul" refers to someone who is yearning or longing for something, typically on an emotional or spiritual level. It implies a strong desire or craving for fulfillment, whether it be love, purpose, or meaning in life. Full definition
We have an unbridled passion for the best drink in the world and are inspired by the desire to share the fruits of our labors with other thirsty souls. (huttonandsmithbrewing.com)