Exercise systems. Whenever you participate in a course such as System Architect Essentials, Pega will provide you with a cloud-based system. Note that this system will be provisioned for a maximum of 7 days after which any changes you made will be lost. I'd recommend this when participating in any course.
Trials. You can request a 30-day trial anytime here: https://www.pega.com/platform-trial. Note that this restricts your use to App Studio, plus any SA-course related material will be absent.