I have not experienced any sweating after eating, but I avoid sugar and all the stuff that you are not supposed to eat post surgery. I also don't drink for 1 hour after eating, but when I drink a bit too early I can tell. It hurts! I have had some health issues post surgery like reactive hypoglycemia and right upper quadrant pain. Sometimes so severe that I end up in the ER. I saw a GI doc and my bariatric surgeon and both suspected it was some sort of nerve issues but it really didn't feel that way. I was put on gabapentin which did help… I got frustrated and took the leap to get an appointment at Mayo. I'm really glad I did. They confirmed what the GI and surgeon suspected that it was in fact nerve pain from having back to back surgeries (Oh, I had to have my gallbladder taken out 4 months after VSG). I was given a trigger point injection and so far so good.
It can be very frustrating, but don't get discouraged. Someone out there is going through what you are and a doctor has seen this happen and can give you answers. DO NOT GIVE UP.