What’s the best way to build up your developers’ creativity skills? Can you share any training programs or projects you’ve found effective?

Coupling real life loss elimination and process optimization processes into our developers' work plans is helping them broaden the knowledge base they need to be equipped for.
This triggers creativity in problem solving, diversity of styles from the very different customer base.
Having developers be part of the solution vs. just developing unleashes their creativity skills along with the process and business acumen opening doors for personal and professional growth.

In my book, creativity skills of a developer can be of two types:
1. Ability to solve a coding problem in a really unique way using some creative logic. This creativity cannot be taught. It is an independent skill that each developer may or may not develop over time. Obviously this skill grows with experience and exposure.
2. Ability to solve a business problem in a creative way. This generally comes from deep domain knowledge. Knowing all the existing pieces of the landscape in and out helps a developer to identify a way he/she can solve the problem either by re-using the existing pieces or by introducing one or two additional pieces and re-using the existing ones.
I do not believe there can be any training that would improve the creativity skills of a developer magically. It is a process over time and each developer grows differently.