Recommendations for SIM Card to work in Switzlerland, Austria & Germany?

WiFi at the airport and at your first hotel will get you started. We pick up a SIM card starter pack (10euro, plus extra time if you want to purchase it.) that is good for a month from the first ALDI we find. It requires a phone call in the local language to ALDI to establish your identity so it is best handled by a native speaker like a hotel concierge, but it is otherwise cheap and easy.

Generally I pick up a SIM in the first country I visit. So lately it’s been a UK provider. What country is the first destination for your friends?

You need to check the fine print carefully. EU regulations changed a few years ago, simplifying SIM card use in Europe since you could cross national boundaries (within the EU) without incurring roaming fees. There are sometimes data caps for this, but I’ve found that it works well.

HOWEVER, since Switzerland isn’t in the EU, you need to look carefully. I found that Switzerland was excluded from free-roaming agreements on most SIM cards (at least, this was true when I did my research two years ago).

Thank you NickB, Rocket, and Melissa for your help and taking time to reply.
Ended up our friends followed one of Rick's links to Lycamobile, which had great features. I called and talked to one of their reps, who suggested buying an unlimited plan (talk, text, and data!) in Switzerland that is currently on sale for CHF 9 (normally CHF39), and then purchase another one once they get into Austria for €9,90, which included 3K mins talk, 3k text, 15GB data, and EU roaming that would cover their time in Germany.

Next time, consider the Dutch Vodafone SIM. You can (still) buy it on eBay, though not as cheap as it used to be. It costs about $20 USD now to buy one on eBay, though it comes with 5 euros of credit and is "activated" for some reason. You'd still need to top it up to add credit so you can activate a data and/or calling bundle good for a month.

But...this SIM has no roaming fees in the EU or in Switzerland, so one SIM would cover all three countries.

I would download Maps.me. It works beautifully offline and uses GPS for navigation. We used it in Cuba where internet access is only available in parks and hotel lobbies and never got lost. As for SIM, if they have a recent phone that supports eSIM, Airalo is a great option. https://www.airalo.com/ You download the app, buy and install the eSIM card, and it automatically activates when you land in the country. They have various packages for different regions and most individual European countries at very good prices. A 7 day pass with 1 GB of data in Germany, for example, is $3 and you can top it off if you need more data. A 30 day European pass is $20 and includes 5 GB. The costs to top off are generally cheaper than the initial purchase. They do not have Switzerland or Monaco in their store yet, although a customer service agent claims they are working on it. Those countries are not part of the EU and therefore, many companies that provide multi country coverage don’t include them. If your friends have a US cell phone plan that will allow international access on a daily basis, they might check into that for Switzerland. We will use ATTs daily plan when we are there later this year and then remove the SIM card when we go to countries with Airalo service.

You can load maps to your phone in Google Maps. I usually do this in the airport before I depart for my destinations. If you are a US T-Mobile user you do get free text and data in nearly all of Europe. Granted it is at slower speeds but it does not cost anything extra. Phone calls are at $0.25 USD/minute. Since I do not consume data the same way on vacation that I do at home this has worked well for me when out of free wifi range.