This is probably stupid and I'm overthinking things, but is it safe to drink after eating protein cereal?

So with the bypass, I was instructed not to drink thirty minutes after eating because it can make you sick. I've encountered this when taking an absent minded drink after eating and when having a drink within the correct time frame but when more full than I realized. So I'm not super eager to experience it again.

I'm about three and a half months post op, so relatively early days still. I had some protein cereal yesterday for the first time. I'd been apprehensive about it initially because cereal is basically eating and drinking at the same time, assuming you have it with milk which I did. It was all fine, even drinking the remaining milk after I finished the actual cereal. But now I'm left with the conundrum of wondering if I should still wait a half an hour after eating cereal to drink something else. I will for now, to be on the safe side. Just wondering what experiences others have had, with this and with other similar food situations.