There are a few possible solutions to tackle a squeaky plastic swing suspension:
Lubricate: Apply a lubricant such as silicone spray, Vaseline or vegetable oil to the swing suspension points. This helps reduce friction between the moving parts and should eliminate the squeaking noise.
Tighten screws and bolts: Check if any screws or bolts are loose and tighten them if necessary. Loose hardware can cause unnecessary movement that can result in squeaking.
Replace worn parts: If suspension parts are worn out, they may need to be replaced. Check the swing for signs of wear and replace parts that are damaged or excessively worn.