"The correct thing to do, even if you don't like it, is to take it, say 'Thank you very much', and then either eat it with a smile on your face, or say you'll keep it for later."
I agree with this answer which was in the comments.
At the risk of sounding racist there is a saying: "Do not accept gifts from Greeks".
"Beware of Greeks bearing gifts"
There are some contexts in which it is inappropriate to accept gifts. In that case you would probably say something like:
"I am very sorry but I cannot accept your gift" or "I am very sorry but we are not allowed to accept gifts".
There is also a problem when something is given as a substitute for a payment. If you have agreed to teach English for a couple of hours you might but unhappy to receive a bunch of flowers for your troubles.
There is an interesting expression:
Cannot be had for love nor money.