200 miles isn’t that long, imo. I’ve done 300 mile rides for the hell of it just riding around the bay area. Things I would bring though:
small first aid kit.
tire patch kit.
small set of tools.
bottles of water.
snacks. You can wear an open face helmet and snack on bugs. They’re high in protein.
coins for a payphone in case you’re traveling in an area that has no coverage
a real map in case gmaps is wrong.
cash for those places still living in the stone age and haven’t heard of debit/cc cards.
Along with that, try to find out the weather forecast and bring the appropriate gear/covering/clothes.