Everyone works differently so this is not a guaranteed solution. I encourage you to try this exercise and make up your own mind about what works for you.
To train your idea muscle you need to push it out of your confort zone. That can take the form of the following exercise: when faced with a question or issue, provide 20 ideas or answers. Do it in a single sitting. The number is supposed to make it really hard to have so many good ideas and allow your mind to look for other solutions, stupid solutions.
If 20 is too easy, raise the number until you have to stretch. You have the right to write down anything, as long as it is somehow related to the issue.
There is a common trait between really good ideas and bad ideas: they both break the rules. Instead of looking for really good ideas, it’s easier to try to break the rules or the norm.
Don’t censor your mind. In my opinion, having a lot of ideas comes from allowing your mind to make strange connections.
Chocolate pond for crocodiles? Sure! Send old people to die in space? Bring it on! Peer to peer dating reviews? I don’t even know what it means but sounds cool! Cars purifying water? Could be the future :)