Hi there, I am currently reaching my 20 weeks and I having the same issues as you since first trim. I can only eat unhealthy food, junk food, fried stuffs, etc. I try to limit those unhealthy food and reduce it gradually (you can still eat the food you like but limit to 3-4 times a week and gradually reduce to 2-3 times then 1-2 times a week). During your "transition" time, try to eat different variety of food/fruits/drinks by re-introducing them back slowly onto your diet. In the end, I have found out that I am able to eat brown rice, broccoli, curry chicken, soya drink, kiwi, apple and passion fruit. I am still eating unhealthy food 1-2 times per week... but take it slow, explore more variety of food!
Try to take in a right amount of veg & fruit that you are able to take too after your fastfood? It's almost impossible to stop people from nagging but try to think of it as their concern & ignore it after. I don't know how true is it that cold drinks is bad for the baby but I chance upon a Taiwan medical video that mentioned cold drinks actually don't affect the baby. Maybe you can try infused water to see it works for you instead of soft drinks.
Try those grilled chicken instead of fried chicken? I too have a craving for cold gassy drink. I drink the new mountain sparkling water (lemon flavour). I try to substitute with healthier option