What does it sound like to speak German with a Spanish accent?
Not sure, but there are snippets of Spanish with a German accent in this video:
Spinach?
As it happens, I have heard German spoken with a Spanish, specifically Puerto Rican, accent. When I was stationed in Mannheim, one of my platoon-mates was from Puerto Rico. He learned German fairly quickly, but just like with his English, he had difficulty in saying the [sh] sound. For example, he would say chip instead of ship. It was odd to me and to our German friends, since he had no difficulties with any other sound. Other than that, I’d say his vowels tended to be shorter in German than a native German speaker’s would have been. He was quite understandable though.
Here’s a six minute interview with ex-footballer become coach Xabi Alonso. He played a few years for Bayern Munich and now coaches Bayer Leverkusen and learned to speak German quite well, but still has a typical Spanish accent (note that he sometimes drops in English words when he can’t remember the German one).
Apparently when Fawlty Towers was dubbed into German, Andrew Sachs (Manuel) did his own dub. He’s German by birth and it was his first language, but doing the recording gave him great pause as to how he would do Manuel’s thick accent and tangled syntax in his (Sachs’) Muttersprache. I’ve never seen that version, but I’d be curious to hear it.
I didn’t know this and I’m curious too. I was too young to catch the original broadcast of “Fawlty Towers” in Germany, but all the reruns I saw were in the original English with subtitles.
ETA: I checked the German wiki, and according to it the show was first aired on West German TV in 1978, undubbed and subtitled, and only got dubbed for the East-German(!) channel DFF, and a second time in 1996 for Sat1. In both cases, Michael Pan is given as the actor who dubbed Manuel. I don’t know him, but it’s interesting that he was born in Madrid (his German family had emigrated from nazi Germany to Spain), so he should have had a good understanding how a Spanish accent works in German.
He can pronounce Vs. My former son in law from Chile pronounced the Arkansas city Vilonia “Bilonia”. My step daughter was afraid the local guys would beat him up.
I thought he’s from Barcelona. 
I don’t know about the Spanish accent like the OP asked about, but I remember visiting Germany and overhearing an Indian woman speaking German. Even as a non-German speaker it distinctly sounded like German with an Indian accent to me.
Don’t mention the war.
Maybe there were two German dubs? I found a video (on FB, not on YouTube, so I don’t know how to share it here) in which Sachs talks about re-recording Manuel. If you google “Andrew Sachs dubbing Fawlty Towers” or something similar, the video comes up.
I watched the FB video, and that’s a real head-scratcher. The video obviously proves that Sachs did dub a German version in the seventies, but according to (German) Wikipedia, it hadn’t been dubbed into German then and only aired with subtitles. Proves that you can’t always rely on Wikipedia…
No, but you can update it for posterity with our find!
I don’t know how to do it, do I have to have an account, or can every slob on the internet edit wiki articles? And I also have no really respectable cite (I don’t think that a link to a FB post counts as a cite on wiki).or more background information that Sachs did the dubbing.
Interesting. I submitted it here (that version is not mentioned in the German wiki page, but linked to in the info box). If they publish it, it should be fine for Wikipedia too.
Is this where the clip is from (mentioned at 17:30)?
Since the FQ has been answered, I hope you won’t mind if I tell some stories about foreign accents.
My wife once heard a man speaking fluent German on a street in Zurich with an obvious Texas twang.
I was once walking down a street in Montreal and was about 20 feet away from a woman speaking what I first thought was British English. When I got 10 feet away I realized she was speaking French, but with a strong British accent.
In my first teaching job at Columbia, one of the leading mathematicians there was the Polish-American Sammy Eilenberg, whose English was excellent, really elegant. There a beginning Polish graduate student there with really minimal English. But he told me that Eilenberg was the one person whose English he could understand.
But the most interesting such story was told in autobiographical book by the Hungarian-American mathematician Paul Halmos. He walked into a restaurant and heard two people speaking what sounded like Hungarian to him. He sought them out and, when he got close enough, he realized they were actually speaking English with strong Hungarian accents. He then backed off a ways and it again sounded like Hungarian. He found a distance at which it was unclear. He actually recognized them. It was Eugene Wigner and Edward Teller. (Side question: Why were they speaking English. Halmos didn’t address this.)