My Type 1 11-year-old has an immediate and significant blood sugar drop from a hot shower, but he is very insulin and glucose sensitive in all environments, more so than the average PWD. Everybody’s experience is different, so what might be a problem for some might not be a problem for you.
Try this experiment: next time you shower, check your BG before you get in, immediately after, and 30-60 minutes later. That should tell give you a rough idea of how much impact the shower has on your BG and how long it takes to show up. Then you’ll have the info you need on YOUR body’s reaction, and can plan appropriately in the future.
Good luck!