I ate late last night. which included a bagel with butter and cheese, and drank soda. then went to bed. today in the morning i felt a sour taste in my throat, like a regurgitation or acid reflux. can this happen or should i be worried?

You could have had a reflux. If you are overweight, losing weight would be helpful. In general is better to avoid eating three hour before bedtime.

Reflux appears likely in the above mentioned scenario with timing (last meal of the day should be at least 2 h prior to bedtime) and content of the meal (soda, gluten and fat based) somewhat notorious for causing such symptoms. Talk to your doc about your symptoms if they persist in spite of lifestyle changes.