^^^
Exactly what sister said
Sometimes when you completely forget it can be a mercy from Allah giving you some sustenance and you can carry on fasting
But if you are aware you are fasting and you drink/ eat or anything goes down your throat including certain injections that will reach your g.i tract your fast is invalidated and you have to make up the fast
If you intentionally break the fast then you will have to do kaffara wich is fasting consecutively for 60days with no break, if you stop for one day then the whole 60days must be repeated from the beginning (this excludes women on period, striaght after period they must immediately carry on their fast)
This just shows how mercifull Allah is to us, but also to not transgress the limits