There are a number of variations to this question but feel free to answer whichever based on your own experience. Some examples:
1) Stripe: showing the code being animated in an IDE with the response https://stripe.com/
2) OpenAI: code that you can copy-paste https://openai.com/api/
Some folks make snappy video demos, other more interactive things. What do you do and how do you do it (e.g. tools, process)?