Dracula wasn't scared of sunlight because of some ancient curse or supernatural weakness.
The guy just hadn't had his morning coffee yet.
Seriously, think about the timeline here. The vampire legend comes from a time before alarm clocks, before corner coffee shops, before anyone invented a decent espresso machine. These folks were supposed to wake up at sunset after sleeping all day in a coffin (which sounds uncomfortable already), and then immediately be charming and sociable? Without caffeine?