Hey there,
My bun did the same thing. I found that using straight up apple cider vinegar was enough to get him to stop. However, once that wears off he was back at it again. So, one day I was at Target in the cheap dollar sections and found an all wooden put together small coat hanging thing (hopefully you get what I’m saying here). I then put that in their cage and got them used to it, then after a few weeks I positioned the toy to the most popular bar chewing spot and zip tied it to the cage. So the little knobs are on the inside of the cage, which they now like to rub their heads on. And it’s prevented him from chewing the bars. He still occasionally does chew on the bars but nothing like he used to. I also found that over half the time he wanted something. Either, to be let out, to have fresh water, or more hay, etc. That was his way of letting me know that he was frustrated.
I would start with using apple cider vinegar on the bars and make sure he’s getting everything he needs at the time of chewing. He might also just be upset that you’re going to bed. Are you his only companion? Because he might just be expressing that he’s lonely and wants to snuggle with you at night instead of being locked in his cage. Or consider getting him a mate.
Hope this helps!