OK, It's a pretty boring journey, for a longweekend, enlivened only by what you MIGHT see and unless of course you really MUST get to Malmo from Calais.
You haven't told us:
(1) When you plan to go
(2) How long you have reserved to ride the 1200 kms between departing Calais and arriving Malmo.
A long weekend suggests to me all of Friday, all of Saturday, all of Sunday and most of Monday. But that could be wrong, as the long weekend might include the time you intend to spend in Malmo itself and - for all I know - coming back too.
(3) You ask for other suggestions 'if there are better places to go for a long weekend's ride, along the same sort of way'? What does that mean? Along the same sort of way towards where? Towards Malmo, towards Sweden / towards Denmark / Germany / Holland / Belgium / France? Or do you really want to go somewhere else entirely?
(4) What made you pick Malmo, as bizarre a destination in Sweden (let alone Europe) as one might think of.
As to: Well, guess again, chum.
Put it into really simple words, what you are trying to achieve, over what precise period and (hopefully) with what aim; to help us to help you. For instance, it's not even clear if you intend to come back to Calais within the same long weekend.
Nah, feck it. It's 1200 kms, broadly NE, set off early, you can do it in a day. Ferry from Puttgarden (check the times) to Rodbyhaven.