Prior to its agreement with PETA, PepsiCo and its partners had funded several experiments on animals:

The PepsiCo Foundation funded an experiment that involved surgically implanting testosterone pellets and human prostate tumors in mice and injecting them with an acid compound. Two animals died before the end of the study, when all the animals were killed.

PepsiCo's partner, Tropicana, funded a student research project that involved injecting 60 young rats with a chemical that causes colon cancer, leaving the majority of these animals to suffer with the disease for seven months, only to be killed at the end of the experiment.

PepsiCo's affiliate, the Gatorade Sports Science Institute (GSSI), funded an experiment in which mice were infected with a respiratory virus and then forced to exercise on a treadmill for more than two hours for three consecutive days, after which they were all killed.
The GSSI funded an experiment in which live rats' hind limbs were cut open from the heel to the knee and their muscle tissue was cut out, after which the animals were killed.

The GSSI awarded several grants to students to conduct animal experiments, such as one in which a student caused rats' muscles to waste away in order to learn how various protein supplements could re-grow the tissue.

They aren't always testing with the drink product. As you can see, they support grants and experiments for various cruel experiments.