Denmark connects to Sweden via the Øresund Bridge which links Copenhagen to Malmo, so if one is not flying, most travel between the two is via car or rail.
@CountingDown - This was a very full day, but we have rented a car in Copenhagen toured Fredrickborg Castle, the Louisana Museum and the Hamlet Castle in Helsingor before taking the ferry across to Helsingborg. From there we drove down to Malmo had dinner by the water and then across the amazing bridge connecting the two countries.
Helsingor to Helsinborg is only a 20 minute ferry ride.
Yes, it really depends on what areas of Denmark or Sweden you are trying to move between in terms of whether driving, train or ferry makes the most sense;
@NoVADad99 , we have taken that ferry between Helsingor and Helsingborg a few times because we have friends that live on the Swedish side. On our most recent trip, we drove north of Helsingor and saw some lovely seaside towns. The beaches reminded me a lot of New England.
We took an overnight ferry from Copenhagen to Oslo during the winter a few years ago. It was the closest thing to a cruise ship I have ever been on. I would love to do that again, only spend some more time in Norway.
There is a ferry that also runs from my husband’s home town in Sweden to Poland that I really want to take one day…I know Poland isn’t on a lot of people’s bucket lists , but I hear it’s lovely there
There are ferries from Stockholm area to Gdansk, Poland; Riga, Latvia; and Tallinn, Estonia. I remember a few years ago a ferry sank on the Tallinn to Stockholm route in a storm with only a handful of survivors.
lj362, go to Krakow. It is gorgeous.
I’m wondering how much public nudity there still is in Scandinavia on nice summer days. Back in the 90’s it was pretty common. People on sailboats in Sweden are often in the buff.
But I don’t recall seeing anything last August when we were there. A friend of my sister’s does go to nude beaches, some of which are public.
My 11 year old son did not seem to mind the topless beach in Copenhagen. 
I guess this would have been 2003 isn.
I was okay with the beach being topless, but found it uncomfortable to walk to the car or stand in line at the snack counter while others were without tops.
“Thank you, God!” (Animal House reference)
Well, it is their boat; they can do what they want. While full-on nudity is rare, it does occur, but generally in places that are off the beaten path. Topless is more common, but not ubiquitous.
Copenhagen restaurant options abound. If you want to splurge, Amass was amazing recently. Great experience, extraordinary food that was interesting, not over worked.
Stayed in the city only, so no itinerary advice. Taking notes for a future trip.
How about some “potty talk”?
Since Norway, Sweden, Denmark, etc, all have their own currency, should we get some NOK, SEK, etc. coins for the toilets before we leave or just use the ATM machines in each country, assuming we will pay to use many of the toilets in several different countries? I worry about not being able to follow directions in a foreign language at an ATM. Also don’t want to have to pay transaction fees at every ATM. We have some euro coins on hand already. The “etc.” would be other countries: Finland, Estonia, Poland, Germany, and Russia.
I think public toilets in Sweden are 5 crowns. It wouldn’t hurt to have a few coins handy but spend them all before you leave. Sweden changes its currency every few years and makes the old bills unusable.
Potty talk part 2:
My bank (Wells Fargo) will only order foreign currency when a minimum amount of $25.00 US is ordered per country. Okay, foreign ATM machine it is.
In 2012, DH and I took a ~12 day trip to Denmark, primarily to visit DS who was working in Copenhagen. My long-time pen pal also lives in Copenhagen, and her parents live about 2 hours north, so we did some visiting and home dinners with them. We did lots of things in Copenhagen which others have mentioned: Nyhavn, Christiania, boat tour, and also rented day cruiser bikes for a couple of days. History buffs enjoyed the Danish Resistance Museum. I highly recommend climbing the tower of Church of Our Saviour, where the steps are on the outside of the tower.
We took day trips by train to Fredericksborg (where we saw a wedding in the palace chapel), Roskilde, Malmo and Lund in Sweden, and a bus to Dragor, a small fishing town south of Copenhagen.This was one of our trip highlights. Be sure to note the gossip mirrors on the homes in Dragor, so those inside the home could discretely observe the comings and goings on the street. Later, we also spotted a few in Copenhagen.
I believe that OP mentioned hiking. Anther highlight of our trip, was a side venture by air to Stavanger, Norway to hike Preikestolen (Pulpit Rock). Google it to see pictures. It was definitely an adventure that we are all so glad we did.