When I was young and had good teeth as well as a ravenous appetite (LOL!), the thing I found to knock down hunger quickly and for a while was a 3 Musketeers bar. They're quite filling to me.
Waffles can do the job too. If you have no idea when the afternoon meal is, make your morning meal based on waffles (or pancakes) to get that bit of extra time in your favor.
Milkshakes will take care of liquid intake, filling you up and keeping the caloric count at a high level. I make mine with a microwave. Get a large cup or glass, fill it up with ice cream, nuke it for 35 seconds, stir it up, add some more, nuke for some more seconds to the consistency you want, add a dash of milk and voila, a quick no-fuss or muss milkshake.
For the whole shebang, get a good half-pound burger, a huge mound of fries, a milkshake and then eat the Snickers bar. If you are hungry later on it will be MUCH later on...LOL!
Rick