Using day-old bread for making French toast is not only acceptable but often recommended. Day-old bread has a drier texture, which allows it to absorb the egg mixture more effectively without becoming overly soggy. This results in a better structure and flavor when cooked. When preparing French toast, the key is to ensure the bread soaks in the mixture sufficiently to achieve a rich taste while maintaining its form during cooking. If the bread is too fresh, it may not hold up well, leading to a less satisfactory outcome. Ideal choices for French toast include thicker slices, such as brioche, challah, or even bagels, all of which benefit from the soaking process. For the best results, consider letting the bread sit out for a few hours to dry out further before using it in your recipe.