Simple/Vague question but what would it take to have a world that oceans aren't salty but sweet? Oceans full of sugar is that even possible?. Also secondary question could life survive in the water?
A Few thoughts:
Unfortunately, a sea of sugar isn't very likely. Sugar would give water osmotic pressure like salt, but sugar is a high-energy molecule that would be a product from a living creature. The sea would represent a HUGE amount of metabolic effort to produce, and a huge amount to protect from things eating it (it's a virtual witch's candy house). So why on any planet would you have an entire SEA of sugar-water?
- Toxicity: The local life isn't like terrestrial life, with very different biochemistry. Sugar is actually the local equivalent of cyanide. The sweet local organism (SLO) that produces it is more tolerant of the stuff than the rest of the ecosystem, but can't actually USE sugar for anything useful. The SLO has been toxifying it's environment for a long time trying to eliminate competitors for space or predators. Over time, it's needed more and more sugar to keep adaptable rivals under control. Sugar would spontaneously degrade when exposed to oxygen, so you might need a reducing environment.
- Lure: Your world contains huge organisms. The sea contains large predators that secrete sugar as a lure. The closer you get to the predator, the sweeter it gets. The sweet-loving prey animal would need to be a high-value target to make the expenditure worth while, so at least Kaiju-big would make sense. Eventually they would get smart and avoid sweetness, so they would need to be rather dumb.
- Amoebic Sea: Your sea represents a part of the biochemistry of a REALLY large organism. Maybe it's using the sea to make vast blocks of alien honey, slowly sweetening it until it crystallizes. What you need vast stores of sugar for is up to you - maybe there's a 30 year hibernation cycle due to an eccentric orbit. Maybe it's energy stores for launching interplanetary spores. Who knows?
- Artificial sweetener: Not all that is sweet is sugar. Maybe the waste product of the local species is a compound that is sweet like saccharine. An artificial (to us, not the locals) sweetener can be much sweeter, more stable, and possibly lower in cost that sugar is. I feel this is a bit of a cheat, but it's probably the most plausible of all these solutions (pun intended).
As to other species, they would need to be adapted to the sweetness, but there is nothing intrinsically incompatible with sweetness and life (except in the sugar-is-cyanide scenario).
The ancient romans used to make syrup by boiling grape juice in lead pots. The resulting syrup contained some amount of a thing called "sugar of lead", which does taste sweet but ironically is a salt.
Sugar of lead is lead acetate. It does not form naturally, but in a fictional world it could be produced by microbes in the water. This would be very toxic and dangerous to animal life as we know it, but in an alien world where this is a thing, the alien life would have evolved to be tolerant to that chemical.
A birthing pool for a megahive
On your planet the dominant form of life is a societal hive creature similar to supersized bees or ants of Earth. From humble beginnings they have scaled up to continental level hives dominated by a single queen and with specialised functions for the workers/soldiers/farmers.
To produce young efficiently they birth young and secrete sugar into major bodies of water so that the larvae can feed quickly once they emerge. Rival forms of life have been exterminated or are so terrified of the soldier caste that they stay away from the tempting sugar seas.