I have a hiatal hernia which causes reflux and heartburn, and my gastroenterologist is the ONLY doc I have that wants me to cut down on nicotine. I told her I have to finish quitting smoking first.
Nicotine relaxes the sphincter muscle at the top of the stomach. That is why they say not to wear nicotine patches to bed, according to something posted on ECF. Basically, nicotine and being horizontal don't mix well. (One fix is to lift the head of your bed, BTW)
My solution so far (which is only partially-working): lower-nicotine near bedtime, and do everything ELSE done does to prevent reflux, like have heavy protein meals early in the day and a light dinner, make sure I have plenty of roughage, and LEARN TO NEVER ADD FOOD TO A MOUTHFUL IN PROGRESS.
I never realized I ALWAYS do that until I was told not to. Chew thoroughtly swallow, THEN add food to mouth.
I also have to move spicy meals earlier in the day, and I have a choice to EITHER eat a lot OR eat spicy, not both.
I suspect I vape too much, too, because I can do it indoors, unlike smoking.
A walk after meals to let gravity do its thing is also very helpful.