Sneezing!!
Sonic- sneezes normally but he’s quills spread out. And if running he will most likely stumble and fall on his face. When he is sick, he often doesn't go on missions, but it is rare.
Sonia- surprisingly sneezes loudly her quills spreading out like sonics, it will throw her off balance if she is not careful.
Manic- sneezes softly almost girly witch he hates. it. "it's ruining my street cred." His quill still spreads out, and his bangs will straighten for a moment.
Tail- his name sakes will fluff out and straightens making it hard to fly when he is sick. He normally sneezes loudly to the point if he is awake working on something and his sneeze echo's it wakes up sonic.
Amy- soft sneeze. Her quills will puff up but go right back to where she had them. It's doesn't affect her too much. But when she sneezes it is a chained sneeze. One after another.
knuckles- Loud and violent. It will make you flinch. It will puff up his quills and jerks his body. He doesn't like getting sick so he avoids everyone sick. He might drop off food to help but he will not step inside.
rouge- She suppresses her sneezes so the most is heard is a huff or a sniffle. Her wings will stiffen mostly but otherwise you will never know she sneezed.
Shadow- Violent sneezer. If it's really bad his quills will puff and chaos control will teleport him each sneeze if not careful.