My scalp smells sweet when not using shampoo

So I shampoo and condition maybe 3x a week, and other days I just rinse my hair with plain water. My shampoo smells sort of like citrus, and the conditioner doesn't contain perfumes so it pretty much doesn't smell like anything.

If I run my fingers through my hair on a day that I've only used water, my scalp smells like strawberries. Even after workouts. My sweat smells normal and my hair isn't oily, so I don't really understand where the smell is coming from. Like I'd expect just normal "skin smell" and not a sweet scent.