Thanks BobF4 for the link! Behold, one of the greatest mysteries in modern cheeseburger history, what a "Cheeseburger in a Can" looks like outside its tin prison. Honk from the SomethingAwful forums took the plunge, bought the cheeseburger, and documented the experience. Honk, you are a pioneer in the fast food world, and for that we are forever grateful.
As I am in Germany I just checked if there is a store carrying these products, and there really is a store having "Trekking Mahlzeiten" just 5 minutes away. So, in my lunchbreak I'll check if they have the canned cheesburger, buy it and open it (and if they don't have them then I will order one). Then I alone will know the secrets what really is in there.
It tastes... not so good. Very bland, kind of like pre-made tomato sauce and a bitter aftertaste.