I agree with the whole grease idea. We don’t eat much fried food, but once in a while fall for the allure and get a bucket of fried chicken. But a few hours later we’re reminded why we dont eat a lot of fried foods. I guess you gotta build up tolerance to it.
Welcome to the community @Vicmac.
One thing to be careful about is that in my experience and a vast array of casual research, is that alcohol-based foods are almost never 100% alcohol free. You didn’t share much, but if you’ve developed a reaction to alcohol, you should know in the US at least, NA beer can contain up to 0.5% ABV. Foods made with alcohol loose a great deal of such in the cooking process, but can still contain enough that people with strong sensitivities can feel unwell, even from what others would claim to be inconsequential amounts. I had a friend who had to be careful with foods cooked with vanilla extract because of such!
Since you had the same reaction though on another occasion where you had just the fries, I still think it’s the grease (see also the upthread mention of additives to the grease which may be a separate issue), and that’s leaving out the possible mental associates with the prior illness that may be making it worse. Heck, I don’t eat pizza to this very day because I associate it mentally with the horrible stomach flu I had as a toddler!