I don't know much about artificial sweeteners so can't say too much - but I don't think they are particularly "bad", though I guess that opinions will vary about how good or bad they are. Generally they have less carbohydrate/sugar content to turn to glucose so from that point of view are unlikely to be as bad for BG levels as real sugar would be. But if it were me, I would really try to get used to having tea/coffee without sugar, because we don't actually need to have them as sweet drinks - and every reduction, however small, reduces the total amount of glucose circulating in the blood - but it's your choice, of course.
As I understand it, the best thing for us is water - and plenty of it, (at least 2 litres per day if possible) to ensure we don't become dehydrated. Perhaps try that instead?