When I did plain water, re-feeds were Hell. I'd be on the toilet multiple times after eating. Now, I'm drinking Snake Juice, or my own recipe of the same thing. That's water with pink salt, NoSalt, Epsom salt. I've started leaving out the baking soda. I add a bit of Borax, but it's not needed. If you stay up on your electrolytes, re-feeds tend to not be as severe. I can go 4 days and eat normally when I break it.
The last 2 weeks, I'm breaking it basically on the day of the Texas game, so I take some liquid Imodium just in case. The food causes a bit of distress, but not nearly as bad as on just water. I'll drink a couple doses of Imodium and be good for the rest of the day. Probably not ideal, but it's worked so far.
I don't get indigestion or reflux when I re-feed. And I'm not gentle on my stomach. I'll break a fast with a fatty Keto casserole (ex: tons of cheese, cream cheese, mayo, cream, chicken and sausage). No real ill effects except you'll have to run to the bathroom an hour or so later, in my experience.