When the Gatorade in disposable plastic bottle came to existence. I thought the bottled version was going to fade soon. Disposable plastic has the advantage of being light weight (reducing carrying cost), has very small chance of breakage, no extra effort in collecting and cleaning use packages for refilling, and it is an assurance that every package is new and sterile. From the customers point of view, the lightness and non-breakable properties mean convenience.
I think several years have already passed and I am still seeing a Gatorade in glass bottle. A bottle of their very own design and branding. It is like a Coca-Cola strategy where both glass and plastic packaging are in use. However, the latter is collecting and reusing their bottles while the first do not. Maybe they do and I am not aware.
Glass bottle might be heavy and fragile but has the advantage of being inert and reusable. It can be reuse as long as it is well cleaned and no breakage. It won’t react to its contents in any way. On the other hand, PET bottles could be reuse but it is not a hygienic practice. It often impart flavor to its contents.