Concerning angels there is only one important rule.

DO. NOT. BLINK.

The original saying is “If it looks stupid but it works it’s not stupid.” There might even be a kernel of truth in there. But to quote the Maxims: “If it is stupid and it works it is still stupid and you’re lucky.”

Edit: I stand corrected on the first part. I still stand by the Maxims.

Just throw them out inside a space suit without any communication devices, if you want them to suffer. Give them some time until oxygen runs out, or they die of thirst, knowing that there will be no help.