Euros in Switzerland

Switzerland does not use the Euro. If you find a place that will take it, it is almost certainly going to be at a severely unfavorable rate.

If you need cash, get some CHF.

And if you do find a place to accept your Euros they will give you change in Swiss Francs

You can sometimes use paper euros but not change. Easier just to find an ATM. If you really have a lot of euros to spend find a bank, hotel, train station, etc to make an exchange. Google the latest exchange rate so you know if they are overcharging. The hotel we stayed at had a decent rate so we swapped enough for small purchases. We always try to come back from trips with at least 20 euros so we have some to start on our next excursion.

I have no personal experience in Switzerland, but based on other euro-border countries, you might find a hotel or other places that advertise their prices in euros for cross-border guests. Some border towns also have dual pricing, just need to do the math to determine if it is fair (Many times they have to hold the rate very close due to competition) But given the ease of getting cash from ATMs and the wide acceptance of credit cards, it should not be an issue.

One thing limiting any problem is that the difference in rates between the euro and the franc have not varied by more than a couple percent in quite a while, they just track pretty close.

Some places do, but it is best to use Franks.

The SBB (Swiss Federal Railways) accepts Euros both in ticket machines and the manned ticket counters.
Some large shops do (Co-op, Migros). In this case the rule is "banknotes only, all change given in Swiss Franks".

In border areas (where I live), and probably in tourist areas you might find small shops (restaurants, cafés, street food stands) also accept Euros. In this case the rate is often 1:1, The current rate is about 1.13, so you are loosing about 13%. Again, it is notes only, all change in Swiss Franks.

In short, never assume a place will take Euros, always ask.

You can use the 1 euro coin to pay for the toilet in the border town Lugano. I saw this 2days ago

I've found several places in Switzerland who take euros, but you'll end up paying more than if you pay in SF.