What can be done with bagel-boil?

I think I'd be more inclined to freeze it to use against the next bagel baking session. Though the idea of using it to spritz over ready to bake dough is also attractive. The alkalinity would break down some of the proteins, leaving the surface of the dough relatively damp and sticky- just like it does the bagels. And that should translate into a wonderfully crispy and chewy outer crust. Not thinking you would want to play with the pH to turn it into a suitable turkey brine solution, or to baste the turkey with. If you did that, aside from making the turkey taste strange, it would certainly mean the drippings would not be good for gravy making. Cooking with alkaline water is tricky, because of how it reacts with various foods. Noodles would get sticky, and veggies mushy - although green ones will be pretty vivid green until the chlorophyll leaches out.

Hi Phillip! Couple recommendations:

I'm thinking you could definitely refrigerate or freeze it and re-use it for bagels (or pretzels!) another day.

You could also let it cool, dilute it with a some more water, and water your plants with the water—baking soda doesn't have an adverse effect on plants, but high levels of sodium do.

A baking soda-forward turkey brine will actually make your turkey taste metallic and won't relax the proteins the same way baking powder would (because in baking powder, there's an acid to balance out the base). That said, theoretically, if you add some kind of acid to the bagel-boiling water, you could probably let it cool down, season it a bit further, and brine a turkey in it. Hope this helps!