Like they are sick in bed and their partner walks into them humming their favorite song. At first their partner feels bad because they think that they feel so bad they are trying anything to feel better, only to be jump scared by the sneeze that suddenly shoots through them and the sign of relief that follows.
Or two people sitting next to each other, maybe at a bus station, and one person has a crush on the other person who is currently trying to fight their allergies. The flowers nearby are just close enough to make their nose tickle, but not enough to make them sneeze. So when they start to tap their nose, the crush is mesmerized by the scrunch in their eyebrows as they tilt their head upwards, voice hitching as they continue to tap the side of their nose. Finally their head snaps down and they sneeze partially into their elbow, more so into their chest. They then sniffle and place a finger under their nose to excuse themselves and apologize about their allergies. The crush is barely gets out the words as their mind is fried and their stomach is flipping.