40 hours is probably not enough to kill your gut bacteria and put your digestive system into deep sleep. Still, my advice is always start with a very small portion of what you want to eat, like 4 big spoons of it, wait an hour, and if it’s all good go for it.
i would just avoid carbs for the next 2-4 days. you will be more insulin sensitive and could get a strong reaction to carbs, which inherently spike insulin and could cause dizziness. im not sure how other people react to smaller fasts, but i know it happens to me, so thought i would share that caution.
A 40 hour fast may not be enough to cause any refeeding issues. However, my previous 45 hour fast, when I broke it I got horrible gas. I took some gas-x pills and I was ok. This fast was a bit longer and when I broke it I didn’t have any digestive issues. (I wasn’t eating foods that are known for causing gas issues.)