There are certain things which you should not do when you are empty stomach, rather you should combine them with some other things or should simply avoid them.
1) Many medicines are harmful if taken on empty stomach, other may not give the results if taken while your stomach is empty. So make sure you eat something first and then take your medicines.
2) If you are not fat then never do exercise before your breakfast, eat something and then go for your daily walk or for some workout.
3) Also avoid only tea and coffee on breakfast rather combine it with toast, bread or something else otherwise your acidity level may increase.