Ordering water in a restaurant in Germany is a bit different than here. You get a glass or bottle of "sprudel" which is comparable to Perrier, seltzer or sparkling water and is available in regular or medium. I'm unclear as to the difference as the bubbles seem to be the same. Perhaps, the sodium content (natrium) is different. It is often listed as "mineralwasser" on the menu. Some restaurants, but not all have "still" water which also comes in a bottle. Tap water, although safe to drink is not commonly consumed. After all, "water is for washing".
When shopping in a grocery store, "still" water usually has a pale blue cap. It's important to read the label and actually see the word "still" if this is what is desired. Otherwise, if it says "Kohlensäure" it will contain carbonic acid. As you can see, it's inexpensive. There is a bottle deposit.
Here's an example of a restaurant drink menu. Schorle is usually a thinned down or spritzer version of a drink. For example Apfelschorle is a popular form of apple drink.
So on my last trip, I learned not to request "Wasser" lest I receive a bubbly, effervescent liquid. Instead, when not in the mood for beer or cappuccino, I asked for "Stilles Wasser bitte". Hopefully, nobody thought I was planning on washing with it.