I’ve used a number of the suggestions given. Sometimes the twisted kitchen roll doesn’t go down far enough so some kind of flexible wire is better.
These type of fridges are meant to be ‘self defrosting’ and the melted ice from back of fridge is supposed to drip down hole at back, into a tray on top of motor, and then evaporate.
OK in theory, but if some food item gets pushed to back of fridge, or a small spill, it can stick and freeze onto wall. Then in defrost cycle, will flow down and block hole. Or, it can end up in evaporation tray at back.
Last year I was trying to track down a horrible smell in kitchen and eventually pulled fridge right out. Found plastic tray full of gungy, smelly water. Nowhere in instruction manual did it suggest that this might have to be emptied or cleaned, or that it even existed!