7 hours in Germany. What are some things I must do?

Eat, eat and eat, and get obese.

It very much depends on where you are in Germany. If you are in Munich you should visit the Science Museum and take a walk in the Old Town. It is also possible to leave Munich to visit the so - called Walt Disney's Ordinary Castle - Neuschwanstein.

7 hours is not a long time to get much done really.   If you could arrange for a 24 hour + delay before your ongoing flight, going outside the airport could make more sense.  Check out were the airport is in terms of Munich centre and add on waiting for a taxi, (and whether the travel would be during a rush hour or not),going through Customs, both ways and I have a feeling much as 7 hours might seem a big amount of time to kill, realistically it's really not much.

You can have a beer in the airport, if that's your main objective.

You could probably buy some beer IN the airport.

Have you looked at a map? The airport is fairly far from city center. Figure at least half an hour to go through immigration (not customs, as you won't be claiming your luggage), then getting a taxi, taxi ride- that's at least an hour. Then you have to go back in time to go through security. It could depend on the time of day and day of the week how long that takes. Allow AT LEAST 2 hours plus the taxi ride back to the airport. Go to tripadvisor.com to get suggestions for places to see. 

go visit a mall or to go the zoo or whatever, just do something fun till you can catch your next flight

remember, IF you leave the airport,  you'll have to go thru Customs AND you'll have to go thru security when you come back ...........