Looking for help with my timetable in Munich

Have you checked the on-time performance of the Euronight train? It averages 10 minutes late and has been as late as 2 1/2 hours in the last month. The train does stop for 1 3/4 hours in Salzburg, so that provides a buffer for delays between Budapest and there.

It does not stop at Munich Hbf, but only at Munich Ost, which is actually more convenient to get to the airport, and there are lockers at Munich Ost. You need to be at the airport 3 hours before your flight, so that means leaving Munich Ost around 10 am. I don't know what there is to do in Munich between 7 am and 10. The Viktulienmarkt opens at 8 am.

First, worth mentioning, you are taking on some risk by arriving the day of your flight. Budapest is a long way away, and given potential delays, mechanical problems, weather issues, labor strikes, if something happens, besides maybe a last minute flight, you don't have many other options to get to Munich. Now 90+% of the time, there are no issues, but I would at least draw up "Plan B", maybe consider changing your flight to the 5th.

But, to your question, if you arrive at 6AM, and need to be at the airport by 11 or 12 (depending if you have a direct flight to the US or a connection in the Schengen area), that gives you 5ish hours.

Your bags you can store at one of the larger stations, they will have lockers.

Maybe the biggest issue will be that at 6, nothing will be open, or at 7, some things at 8, some cafes and restaurants at 9, shops and stores maybe 9:30 or 10.

In early December, wandering the Englischer Garden, which would be a nice activity before a long flight, may not be as fun depending on weather. So I likely would head to the Marienplatz area, wander around, get some more pictures without the crowds. Some of the churches might be open early for at least entry and a look as well.

By 8 the stalls at the Viktualienmarkt will be opening, for something to eat or last minute souvenirs. At 9, you should be able to find someplace for more of a meal, my "go-to" place would be the Schneider Weisse Brauhaus for the classic Munich breakfast of Weisswurst, Pretzel, and a hefeweizen beer (they have other breakfast options as well). After that, you might be able to hit a shop or two, before finding your bags and getting to the airport.

I second the Schneiderweisse Brauhaus AND the Hefeweizen. I did that for lunch yesterday. The Munich Marathon was running past the front door. The oompa band was playing at the table next to us. It was all perfect. Just ignore the MacDonalds and pizza place across the street.

Does anyone know where one could get a shower? That would be my issue.

I suspect there is not going to be as much time as you would like to hope there
would be... By the time you store luggage and navigate from Ostbahnhof to
Marienplatz or someplace nearby, it's probably 7. Give yourself 90 minutes
to depart downtown, stop at Ost, gather your bags, and take the S8 to the
airport. So you have from about 7 to 9:30am.

If you have options like carryon bags, business class, EasyPass, that might
give you more of a buffer from the 3 hours that everyone recommends. But
probably no more than a half hour extra.

And, if it were me (or Mr E), I would want a shower after an overnight train and
before a transatlantic flight. If you don't have lounge access, there are showers
available at the airport:

Showers at the airport

I think the suggestions downtown are fine, but you should be prepared to abort
and err on the side of caution.

Personally, I would drop a day off of Budapest (sorry Mr. E) and get to Munich a day earlier. I would get little sleep as I would fret over every stop and potential delay.

jkh, I am going to be more extreme than you. The OP is finishing a tour 1 December and wanting to be on a flight in Munich on 4 December. UNLESS you paid the $250 fee to change your flight from Munich to home to Budapest to home (probalby with a layover in Munich). Just not worth the hassle for 2 days and the risk of missig a connection.

Without too much time that day, you could have a relaxing time going to Freising, which is a charming town 10 minutes from the Munich airport. There’s a lovely old town, a beautiful cathedral, and an acclaimed museum which has a permanent exhibition from the US light artist James Turrell, along with other contemporary artwork and historical work. And a friendly cafe, the Q-bar!

OP here. Thanks to everyone who weighed in. I'm understanding that the amount of time we have on that day is not all that long, given possible delays, etc. I think we will stick with our plan and, if the train is on time, we'll just be ready to fill our day with whatever open activities we can find before heading to the airport...or we'll just go to the airport early and hang out there (showers, restaurants, shops) or maybe visit Freising (thanks, Tinka) if there's time.
If we do want to do something like the Freising outing, my hope is that we are able to check our luggage early at KLM, which I'm told is sometimes possible there.
Danke.

That's funny, Freising just came up in another thread. A suggestion was to take the bus to the world's oldest brewery, Weihenstephan. From 1062 A.D. Have a nice meal at the Braustube there. We did, and the t-shirt is in my bag, to be worn tomorrow.