Uppsala or Vaxholm on a Sunday?

Things are generally open on Sundays in Sweden, sometimes with slightly reduced hours. If there is something specific you have in mind, just check online. Either place is a nice day trip - Uppsala has more to see and do. It is a lively university and cathedral city and you can also visit rune stones and nearby Gamla Uppsala (ancient burial /Viking site); Vaxholm has the scenic ferry trip and is more of a quaint harbor village plus the fortress - though you'd probably want good weather guaranteed. So just depends if you want the historic student city feeling + Viking history or small town archipelago atmosphere.