The simplest way to make sure that French toast does not become soggy in the middle is to be careful how long you soak the bread in the batter before frying. While you need to allow the bread time to absorb the batter, if you leave it to soak for too long it will become soggy. Also consider the ratio of eggs to milk in the recipe you're using. Eggs help to thicken the batter, so a recipe using a ratio of just one or two eggs per cup of milk is more likely to create a soggy French toast.