Both alcohol and nicotine. Corona probably saved me with its lockdowns (though I did go back to hard drinking to some degree after). I still have the odd drink and odd cigarette, but neither are everyday things for me anymore and I can go weeks without either (though on days I do drink, it certainly makes me want to smoke).
Currently battling coke zero. I will dehydrate rather than just drinking plain water (carbonated makes little difference) as I just don't want to drink it and forget about it. As a kid, the place I lived had well water that didn't taste great, so that's probably something to do with it. I've managed to somewhat replace it with a zero-calorie sports drink powder that I put in water. Still, it lacks the mouthfeel and satisfaction.
The other current battle is gluten and thus wheat and everything containing it. This is more-or-less impossible here in Japan if eating out (most soy sauce has gluten). The background is that I likely have Celiac's (dad has it with very rough symptoms starting in his 60s, I'm in my 40s and a DNA test already told me I had inherited markers for it was likely to develop it). I was called "the bread kid" as a child because of how much I liked to eat (particularly homemade) bread. Until very recently, I baked bread and stuff a lot. It really sucks because I really miss the texture and taste of good bread. It's also difficult when thinking about what to eat. "Oh, I've got some pasta that will just take a few minutes to cook" is not a thing anymore. I have to make rice or potatoes ahead or have nothing but meat and veg.