It appears that you have had a sudden onset of having a sweet taste in the back of your mouth associated with weight loss. The most concerning of these symptoms is the sudden weight loss which could be secondary to a serious medical condition.
A sweet taste in the back of the mouth can be caused by medications, artificial sweeteners, dental issues, or medical conditions such as diabetes and gastroesophageal reflux disease (GERD).
One condition that comes to mind that involves both sudden onset weight loss and a sweet taste in the back of the mouth is diabetes. Excessive urination, excessive thirst, and sudden onset weight loss are all signs of diabetes and requires immediate medical attention.
In your case, the most concerning issue is the sudden weight loss and sweet taste which may be an indication for uncontrolled diabetes. This requires immediate medical attention by your primary care physician or a visit to the local emergency room without delay.