when a supervisor gives unsolicited advice on how to do something as a reminder and you have been doing this job just that way for the last twenty years and you want to say ...really for real you are advising on that? Do you have any puns or sarcastic sayings that you could joke around with your co workers so as not to be so offended??
Be careful with sarcastic remarks about your supervisor because there is always a chance he or she will find out what you really think. Anyway, here are some options:
Oh, it's so kind of him/her to teach me!
How sweet of him/her!
I'm so grateful for his/her helping hand!
What would I do without him/her?
He/she is such a help!
He/she is such a lifesaver!
Please note that all of the phrases above can be used not sarcastically and mean sincere gratitude. But sarcasm is a kind of irony, and your listeners will hopefully understand that you are not that serious thanks to the note of sarcasm in your voice. So your intonation and context really matter!