I normally add a few pinches of cinnamon for sweetness. But some people add sugar and/or vanilla extract to the mixture too.Basically, but every time I've looked up French Toast and see maple syrup, cream or fruit and I just assume there must be some extra ingredient or something that makes it something sweet?
So yeah, it's really just the five ingredients - bread, butter, cheese, milk, eggs.
Put butter on bread, put cheese between buttered bread and close (forming a sandwich), mix 2 eggs and a splash of milk with a fork in a larger than bread sized bowl, soak sandwich in egg mixture for 30 seconds to a minute, put butter in a saucepan, turn stove top on, place saucepan on stovetop, get it hot then reduce the temperature, put egged sandwich into pan - heat until lightly brown, flip, then heat until cheese is melted inside. Then remove from the pan, cut it diagonally, then eat.
Never had it with cheese though definitely going to try it out now that you've mentioned it.