These workshops are often best when competitive. Split them into groups of roughly 4-5 people (allowing for larger teams if your number of groups reaches a dozen) and have them build a startup by designing an app that "uberizes" an industry that everyone is familiar with. Some good examples here are grocery delivery, lawn care, corporate chef service, hardware as a service, or babysitting.
Give them a discovery phase where they can speculate broadly about customer needs and then have the teams discuss together what each team's ideas were. Score each team's input, pointing out any obvious flaws to course correct and a strength of each. Explain pivoting and how we need to adapt to change and learn from competitors, the market, and consumer trends. The teams revisit, change their plans, and come up with a more solid idea. Have them draw the home page of the app with markers, suggesting that having multiple variations is okay. Have the teams come together again to reveal their work and score them again. Point out areas where each design didn't meet a given KPI according to fake data. Give them another round to adapt and change before coming back to final scoring. If time allows, add more rounds in the middle to adapt to new changes and conditions. Add a new federal regulation that throws things into chaos. Add a new tech platform, the app needs to work on VR or Amazon Alexa now.
Hopefully, some of this can help. The question is a bit subjective, but it's an important question nonetheless.