After I purchased a Bread Machine, the next year (early 90's-pre-internet era) I was given a Bagel Machine. Mine came with a video tape with a lot of detailed information and mentioned soft pretzels if I remember right. The dough would be made in the bread machine, rolled to form the bagels then the bagel machine did the rest.
I think the hot water step for pretzels mentioned adding baking soda to the water and use the machine's metal spatula to float the pretzels in that hot water bath for a minute. I've since learned that food grade lye is used by commercial bakers to achieve the results they desire. (if you wanted to try this outdoors, where it would be safer, wear protective equipment as the lye is much stronger than baking soda)
What this does for commercial bakers is to caramelize the outer surface of the pretzel so it will be chewier and bake to that dark brown color. The center of the pretzel may also be more dense and chewy. At home the pretzels will be lighter in color and texture as baking soda is not as strong as lye.
If I were to try this using food grade lye, I'd use the plastic spatula, and a wooden draining rack on a surface that wouldn't be harmed by the lye.
Then these would be salted and then baked to that characteristic color.
Where the pretzel differs from the bagel is the hot water for the bagel has malt syrup and even sugar added to it. Both pretzels and bagels sit in the hot water for about a minute. I don't remember the exact amounts of these additives that went into the water though.
When I showed this Bagel Machine to friends, they thought it was a deep fryer. It looked like an over grown bread machine. The handle which extended out from under the lid served as a large spatula for dipping the 4 bagels into the hot water bath and then served as the baking rack. (or pretzels if you wanted to make those) Then the hot water was drained and the chamber became an oven for baking. It was kind of a novelty gift and they weren't on the market too long as I remember but still are available today on eBay.