I have flight from Frankfurt to Dhaka via Istanbul and i would like to take some chocolates. As I'm travelling light with only hand luggage, I was wondering if there is a restriction on how much chocolate I can take in hand luggage.
The governing constraints would be:
The volume and mass allowed by the airline for carry-on baggage for the flights in question.
Whether the item is allowed into any intermediate country where you are in transit, especially if you need to clear customs etc. in the intermediate country.
Whether the item would be allowed into the destination country, either in whole or up to a limit.
The import duties on the item and the cost-benefit analysis performed by you to determine whether this is worth it, including the opportunity cost of not using the money for some purpose other than buying the chocolate and the forgoing of taking some other item with you by occupying the space in your carry-on baggage.
You would research 1 by consulting your airline's website.
You would research 2 by both consulting the airline's website and the website of the transit airport. It is possible that you would not need to clear customs while in transit within a terminal but would need to do so if you are transferring to another terminal.
You would research 3 and 4 by consulting the appropriate website for the destination country's customs service.
There's nothing magic about some item being brought by checked-in or carry-on except those things which are expressly forbidden from one but not the other or both.