I would test before and two hours after a meal when having a regular sandwich to see how my blood glucose reacted to that particular meal before deciding it wouldn't hurt because the rest of my diet is ok.Id recommend unless on a strict low carb diet of under 50 or under 50 carbs then have your sandwich just don’t hammer loads of them
A bacon sandwich as a meal won’t hurt in the big picture if the rest of your diet is ok
If you are keeping to under 50g/30g - good at sandwich - fry up some bacon and eggs and enjoy with no bread