Welcome to the ECF. Depending on how long since you quit smoking, your taste buds can get more sensitive so the liquids actually may have a bit more sweetness than you perceive. With that caveat in mind:
some are much sweeter than other depending on the vendor. Often you can tell how sweet it might be by reading the product description and, especially, any
reviews.
An option you may try if the liquid you get is definitely not sweet enough to your liking is add a (tiny) bit of sweetener to the bottle itself. Many people will use Maltol, or you can find diluted Maltol flavors such as "Cotton Candy" and the like to give you the sweetness you seek. Some people add "direct" sweeteners (again in very small quantities). Personally I use Splendex, but there are many other sweeteners recommended - check out the DIY section to see if you can improve what you have during the time that you can find one that is to your liking without any modification.
Good luck!