They do make window units for sliding windows.

Sounds like you have "casement" windows. I'm not aware of any window units that will work with these. You could try a portable unit that exhausts the warm air via a duct through these windows.

Casement Window Air Conditioner

"A casement air conditioner is similar to a window and wall air conditioner with one big exception: they are meant for use solely with casement windows that swing out to the side or slide open sideways. They are tall and thin as opposed to traditional window units which are short and wide. They’re also much more expensive and less energy efficient than window units at the same Btu rating.

Overall, the use of casement air conditioners is limited to room situations that rely solely on casement windows. Actually, we think that a quiet portable air conditioner is a better option for a casement/sliding window. Portable air conditioners offer a flexible cooling solution and they also have a lower price than casement air conditioners."

Having had some experience with portable units, I would *NEVER* choose a portable if there's *ANY* way to install a window unit.