Service is usually very good. If you get someone unsure of "Gluten Free" ask for manager. He or she will turn it into training opportunity. [We win twice!] If you have knowledgeable person go for it! They have three (3!) pages of Gluten Free foods, toppings, & (of course) frozen Custard.. Our favorite is hot Fudge Sundae with Red Raspberries. But, look at list, & find your favorite. Sandwich: I love double burger on GF buns ($1.25 upcharge) with everything. Wife single no tomatoes. Sadly, fries are cross contaminated.
When I asked for a gluten free bun, the employee asked me if they should mark my order as a gluten allergy. Because it was marked that way, my food came out on a tray separate from the other diner in my party who had ordered gluteny food. The bun came in it's own sealed package. I did not ask about a separate fryer, as I selected plain mashed potatoes for my side. Thanks Culver's!
They usually have gluten free buns, they will usually put your GF burger makings in a box and let you assemble it yourself, this does give confidence since the bun is kept in its own individually wrapping. But they have been out of GF buns one time when we were there.
Mostly we go for the frozen custard. Asks for your concrete mixer with a gluten allergy and they will clean off the machine before mixing it for you.