Your agency may have stricter rules regarding gifts. The meal is offered during a meeting you are attending for official reasons. It is the customary practice to hold a meeting over meals and your paying would be inappropriate. The meal is offered at a company cafeteria where there is no public price structure. A. Gift giving among co-workers during holidays is fine, but between superiors and subordinates, it will be a problem unless it is very inexpensive.
Some agencies have stricter rules.
I will be getting married soon and will invite friends who work for various firms that do business with the City. A. Customary gifts, for social occasions, such as a wedding, are generally okay. This goes for gifts between co-workers and between City employees and friends at firms doing business with the City. But the gift must be a reasonable one, and it must be clear that the reason for the gift is the friendship, and not the business relationship. As part of my City job, I have to travel to a firm my agency is doing business with.