Making an inflatable slide slippery without using water can be achieved by using alternative materials or substances that reduce friction. Here are a few methods:

1 Soap or Lubricants: Applying a thin layer of mild soap or lubricants on the surface of the slide can reduce friction and make it slippery. However, ensure the soap used is non-toxic and safe for the material of the inflatable slide. Test a small area first to ensure it doesn't damage or degrade the material.

2 Vegetable Oil or Baby Oil: Similar to soap, vegetable oil or baby oil can be lightly applied to the surface of the slide to create a slippery surface. Again, ensure the oil won't damage the material and test a small area before applying it to the entire slide.

3 Silicone Spray: Silicone-based lubricants or sprays specifically designed for reducing friction can be used to make the slide surface slippery. These sprays can create a slick surface without damaging the inflatable material.

4 Talcum Powder or Cornstarch: Dusting the slide with a thin layer of talcum powder or cornstarch can help reduce friction and make the surface slightly slippery. However, this method might not provide as much slipperiness as other substances.

Before applying any substance to the inflatable slide, it's crucial to test a small area to ensure it doesn't damage or degrade the material. Additionally, make sure that whatever substance is used, it is safe for use by individuals sliding down and won't cause any allergic reactions or skin irritation.

Always follow the manufacturer's guidelines and recommendations for cleaning and maintaining the inflatable slide to ensure its longevity and safe use.