Put anything you want into the bag.
Anything you think you might need for the last 40 miles of the ride and don't want to carry for the first 50 miles is perfectly fine. As long as it fits in the bag it will be OK. Food and drink are typical - a couple of bottles, some bars, gels, etc.
You could put a couple cheeseburgers and french fries if that is what you want. I saw a can of coke in a drop bag and met someone who sent an 8 oz container of pickle juice ahead. I sent a small Boars Head Ovengold Turkey and Smoked Gouda wrap once - only about three or four bites but it was really good half way through a hard race.
Things like empty bottles can be put back into the bag for retrieval at the finish line. Keep in mind that it sometimes takes a lot of time for the bags to make it back and if you are fast, you might be waiting around.
-Tim-
Last edited by TimothyH; 09-02-19 at 08:18 PM.