Well, we can actually tell from this grocery shopping list written by Michelangelo himself in the 16th century. He ate anchovies, bread, two fennel soups, a herring (un aringa), four anchovies, tortelli, and wine (“un bocal di vino”), among other things. He drew the list as pictograms because his servant was illiterate. He would tell him what he wanted, "get the big loaf of bread, not the small one", but also sketch it so the servant could look at the images to refresh his memory while at the market.
Experts say the list is for three separate meals. He drew bread rolls as simple circles--an easy shape for his servant to remember meant - bread. For another meal, he wanted two rolls but for another, six. The herring is sketched by itself, and bowls are filled with salad and anchovies. Two dishes of stewed fennel are shown side by side (perhaps he wasn't dining alone?). For the wine, he drew a small wine carafe next to a larger one--perhaps two types, one being an after dinner, sweet wine? The tortelli (tortellini) pasta were not drawn at all. Perhaps his servant's wife made them, something he obviously would never forget if the Master asked for some.
During this same year, Michelangelo had ordered many of his notes and sketches to be burned--the Renaissance method of shredding documents. It's amazing that this little take-out order managed to survive at all.
This grocery list is archived at the Florence museum Casa Buonarroti, where one can find many of the artist’s handwritten notes, doodles and sketches.