Coach or minivan tour to Normandy from Paris

some take the train to Bayeux or Caen from Paris and pick up a tour there
https://www.overlordtour.com/

Taking a coach tour all the way from Paris will lead to a lot of time wasted on the highway. If you really cannot afford to spend even one night in Normandy, I think the best bet is probably a tour offered by Overlord Tours designed for folks staying in Paris. It picks up at the Bayeux train station rather than downtown (saving some time) and departs just a bit later than the regular tours depart. As a result, it's possible to take an early train from Paris that day and catch the tour at the Bayeux station. (Of course, there is the one-hopes-only-theoretical possibility of a train delay.) Since you travel to Bayeux by train (faster) rather than bus, that means more time for seeing the D-Day sites.

Note that the tour cost (95 euros) doesn't include the train ticket. You can potentially save a lot of money by buying that train ticket very early, but such tickets are non-refundable and non-changeable.

As far as I know, all of the Overlord Tours use minivans.

You can't possibly spend just 1 night in Bayeux???

When my May trip got overtaken by a wedding I decided to do Normandy day trip via City Wonders. Will report back at the end of May on how it goes.

Agree with Tim...is there any way you can spend a few nights in Bayeaux? You will barely scratch the surface on a day trip; it will be a "check the box, I've been there experience." With that said, if I truly only had time for a day trip, then I would take the train to Caen and hire a private guide who could tailor the tour to my specific interests.

When we did a (informative, fantastic) day tour with Overlord Tours several years ago, we saw huge bus groups with one guide and wondered how much they were actually getting out of the experience. The groups didn't look like happy campers. So if you have only one day, acraven's train+Overlord Tour is best, followed by a minivan tour.

Or you can stay overnight in Caen and join a tour of the WW2 beaches. You might be able to get back to Paris by train the second night but it will be a stressful rush. Road time to and from Paris will be at least four hours each way. The train is not super-fast but more comfortable and staying two nights will give you a much fuller experience, especially on a full-day tour with an expert guide.