Best of a weekend in Hamburg and Berlin?

Greetings!
I had 5 days in Berlin and still didn't see all I wanted- will you arrive there Sunday morning or have stayed overnight from Hamburg?
A surprising highlight was the Trabi Tour:
http://www.trabi-safari.de/index.php?language=en
I was afraid it would be kitschy but it was fabulous. (I was fortunate to have an electric one!) The guide was informative and humorous plus you drive past iconic sights in the process. It's not far from Checkpoint Charlie (that small museum was interesting, too).
You'll need an early start to the day, but could see the government buildings from the outside. And the Holocaust Memorial.
Touring the Eastside Gallery Wall was memorable, too. Since these are all almost entirely outdoors, that should help with your compressed time.
I'm sorry I can't help with Hamburg. Have a wonderful trip!

Hamburg has arguably the largest model railway in the world (Miniatur Wunderland) - we were there for most of the day.
During our weekend, as well as that, we had a harbour boat trip, went to the opera, visited a museum of illusions and had some good meals.

I would just make a list of places you want to see, group them geographically and see as many as possible. If it were me, I would probably spend the most time in Berlin, as it has so much to see and do. Hamburg is a cool city, but Berlin is really incredible.

Keep in mind that most shops will be closed on Sundays by law in both cities, although they will be open at the Hauptbahnhof and other transport hubs.

suggestions about how to make the most

Define content of most, e. g. interests or not-likes. And which weekend?

Hamburg wasn’t our favorite stop for two days but that was just us. Two hours of miniature trains was more than enough though many folks spend the entire day. A very pleasant surprise was to discover Lüneburg about 20 minutes away by train where we spent our second day. It is perhaps the most beautiful small town we have come across in many years of travel. I’d prioritize Berlin which has so much to see. Different strokes as they say. Safe travels

here's one way to do Berlin - 36 Hours Berlin

For Berlin, to get a sense of the city, you might follow the Rick Steves walk along Unter den Linden. While near the Brandenburg Gate, if you can get tickets in advance, visit the Reichstag dome. Then visit the Berlin Wall Memorial if it's of interest, and then to Alexanderplatz to see Berliners out enjoying their Sunday.