Can i test the glucose level after drinking coffee? and is it ok to drink coffee at morning before breakfast, and before my insulin and sagimet ?

If you test your blood sugar after drinking coffee with sugar in it, then it will not be a fasting blood sugar but it will be a random blood sugar. You can still do this and then take your medicine after you have the coffee. Likewise, if you drink it with milk or cream, it will not be a fasting number. You can take your medicine after you have your coffee, regardless of what you put in it.