Overnight in Munich

I would go to the Marianplatz and the Deutches Museum.

The Hofbräuhaus is the big touristy beer hall, and it would be fun. All beer halls are better if you learn the words to "Ein Prosit" before you get there.

If he's by himself, consider signing up for a pub crawl, so there would be a group to tour around with.

Arriving at 7pm then departing the next day at noon? Not time to do much I'm afraid.

Depending on how fast you can get out of the airport and on an SBahn it can be 1-2 hours before you are in the city center. That's 8-9pm and just enough time to grab a beer and a bite at Hofbraühaus or another beer hall before checking into a hotel.

For a flight at noon I'd plan on leaving the city center at 10am (and I cut it closer than most). That's just enough time for a nice breakfast of weißwurst.

DJ

Is he planning on sleeping? In downtown? Near the airport? A lot depends on that.

I wouldn't cut it as close as DJ. I'd allow 2-2½ hours at the airport before departure. If he stays in town, near Marienplatz or the Hauptbahnhof, it will take about 45 minutes to the airport, so I'd leave downtown Munich no later than, say, 9 am.

He has 17 hours in Munich, but about 8 hours will be spent checking in to a hotel, sleeping less than 8 hours, and checking out, so he's down to no more than 9 hours, and it take 1½-2 hours just for the trains to/from the airport.

I agree he should spend his time seeing Marienplatz and eating at a biergarten (preferrably Hofbräuhaus).

There are sleeping "pods" in Munich airport. I wouldn't bother renting a hotel. Let him still out until he's finished then head to the airport to get a bit of shut-eye in a sleeping pod. The Munich airport is really quite nice!

That happened to me on a trip seven years to Munich, except it was arriving in the late afternoon, ca 4 pm and leaving the next morning at ca 9 am. I stayed at the Wombats hostel then. If something similar were to happen now in Munich, I would stay at the Pension at the main train station, take the S-8 to MUC at 06:30

All fantastic tips, I appreciate the time and effort to respond. I'm interested in the sleeping pods...he'll have to set two alarms though as he isn't a morning person 😴

Sleeping Pods: http://www.munich-airport.de/en/consumer/aufenthalt_trans/hotels/napcabs/index.jsp

After reading the others input and thinking about it more I'd recommend the following:

First, since time is precious, get familiar with the airport layout, the areas of the city you plan on exploring (Hauptbahnhof area, city center), and the public transport schedule. Print maps and schedules if you won't have access to a working smartphone and internet. If you have a smartphone with Internet access you can save time by purchasing a transport ticket with the MVV app. On the day you land a day pass will be best as you be taking at least two trip and probably three. But most important is studying and being familiar with this info before you land, don't assume you can figure it out once you land.

Second, have a plan with contingencies in case something goes wrong. I'd recommend dropping bags at hotel/hostel (I also recommend Wombats) then heading strait to the biergarten at the Viktualienmarkt for ONE beer then walk over to Hofbraühaus for the beer hall experience. If the weather is rainy then just head strait to the Hofbraühaus. If for some reason the Hofbraühaus is too crowded have a back up beer hall identified (I'd recommend Hofbraükeller). Don't overdo it in the evening if you can.

Last, a breakfast of weisswurst and weissbier is recommended. If you don't eant to cut it close like I do you can have this at the airport at Airbraü.

Hope he has fun.

DJ