Think for a moment(s) about what you ate yesterday. Make a quick list in your sketchbook if you need to, but today's sketchbook is all about food. Think about one of those things/meals and choose a complex-ish item or items and draw it/them from memory.
Your drawing should be detailed - so a slice of plain toast is probably not the best option. Ideally I would see you draw straight in pen, but if that makes you totally uncomfortable a pencil is just fine.