A direct translation doesn't really work here - unless you actually are talking about packaging, in which case "deceptive packaging" would be fine. The closest English term that I know to describe the concept of "Mogelpackung" is "window dressing".
From the Islington council (UK) website -
What is the law on deceptive packaging?
Deceptive packaging is when goods are packaged in a way that makes the product seem larger or better than it really is.
Trading standards officers have used the provisions of the Trade Descriptions Act in the past to tackle the problem. However, recent European regulations encourage manufacturers to address the problem of wasteful packages and how its disposal will affect the environment.
Deceptive packaging is commonly found at Easter time on chocolate eggs but can also be found on some cosmetics and perfumes.
"Mogelpackung" means literally "deceptive packaging". However, it is usually used in the figurative rather than the literal sense, often in political discussions. Thus, for example, a political party might be promoting a draft law which allegedly has the prime objective of combating terrorism but when one reads the draft carefully one discovers a paragraph drastically limiting the number of foreigners allowed into the country. It quickly becomes clear that the objective of the law is to prevent immigration and not to prevent terrorism. The opposition parties will cry "Mogelpackung !".
Another translation of "Mogelpackung" might be "trojan horse" (in German "trojanisches Pferd").