how come PETA doesn’t do anything about the thousands of alligators that are killed every year to make Gatorade

Probably because Gatorade is not made from alligators

"Gatorade Thirst Quencher contains water, sucrose (table sugar), dextrose, citric acid, natural flavor, sodium chloride (table salt), sodium citrate, monopotassium phosphate, and flavoring/coloring ingredients; some Gatorade flavor variations use brominated vegetable oil as a stabilizer."

I don't believe they use any alligator products in that. 

They don't kill or need to kill the gators because all that is required is to collect the gators' fluid discharge.
It only requires about a pint of gator fluid per batch of gatorade is adequate to give you the energy fix you need.  This post was edited by Kittigate at March 5, 2018 7:54 AM MST

and the hundreds of humans who are skinned alive each year and hung on hedgerows to dry in the sun for humane reasons. 

They do.  They drink the first batch of Gatorade.  Then they PEE ta fill the empty bottles.  This pee is then sold on the store shelves.  That is why Gatorade tastes like piss and salt.

It's bad for you.  Don't drink that bilge water.