I'm starting to do single day trips quite often and was wondering what is suggested to carry around in a backpack/daypack if I'm just visiting cities for a day. All that I can come up with is a small first aid kit and a water bottle.
My typical trips would be to fly out on the first flight in the morning, take public transit or a taxi from the airport into the city, go sightseeing and fly back home on the last flight of the day.