How to pronounce “thwack” in English

As I inhaled another series of quick, shallow breaths to try to calm my nerves.I turned toward my tormentor to accept my fate, just as a colossal was of spit flew through the air and landed with a wet, dewy thwack dead on my cheek.Hushed silence, except for Jake, whose loud, guttural snort only meant that another loogie was imminent.