What might happen if it rained there?
It would largely depends on how much sugar and how much rain. Some people have brought up it would be like rain in a salt flat, however, this is more twards the extreme of virtually no water. For the other extreme you might want to check out the Dead Sea
which is a body of water near Israel that is in a perpetual state of max saturation. For one, swimming in this water is odd because you float way way more than in regular salt water to the point where you would struggle to submerge yourself if you wanted too (you don't cause the salt would burn the piss out of your eyes and nose).
In the case of sugar you would also achieve a max saturation point eventually and due to its crystalline nature it would prob form very similar formations near the shore line. The bottom would most likely be very hard w/ a squishy silty layer of sugar that is right on the boarder of dissolving or coming out of solution due to the temperature of the water.
The main 2 differences would be:
- Sugar is sticky which would add an interesting dynamic on attempting to swim in it
- There is also the difference that the Dead sea has such a high salinity that only a handful of bacteria can survive in it. Sugar on the other hand would cause all types of bugs and bacteria to swarm.
If we assume the sugar is endless, what would it look like during a rainstorm?
Its not so much the endlessness of sugar but rather the ratio of sugar to substances the sugar can dissolve in. The Oceans of earth have 38.5 quadrillion tons of salt ... but since there is more water than salt its all dissolved. If the ratio was skewed the other direction you would have crystalline surfaces of salt (or sugar) with puddles of water that are in a perpetual state of evaporating and being absorbed (think of a salt shaker in a place with extremely high humidity).
Another aspect would be ... what about wind? There would most likely be erosion due to wind as well as water. You would most likely get dust storms of powdered sugar and rain drops that contain trace amounts of said sugar dust before it even hits the ground.
And would the aftermath be when it clears?
Again, I would prob reference the shores of the dead sea:
This is Crystalline salt that is left along the shore as the water evaporates out of the salt. A very similar thing would happen with sugar ... though there would be much more life attempting to devour it.
I would highly recommend considering the water cycle as a whole instead of just what happens when it falls from the sky. Also, the microbiome of the place (all the bacteria) would be insane. You would have billions of strains of bacteria waging full scale war on each other with all the free energy laying around.