Today I served a customer dressed obviously for cycling. He came in with his trousers tucked into his socks and a very obvious cycling helmet.
I asked my colleague
Do you think he came on his bike?
She (is Polish with exceptionally proper English and) asked me how I would refer to a sarcastic question like that. Nearest I can think is rhetorical?
Best Answer
The device you might be using is an understatement:
In this case, not only did he come on a bike, but he is apparently a very enthusiastic cyclist.
Your question also might be considered sarcastic if your intent by it was to mock the way the person was dressed.
Irony is something different, where a statement of fact seems at odds with other facts:
There is no irony in your question (rhetorical or not) that suggests that there is a disconnect between what you are observing and how the person is dressed.