Sheet to JSON is a Google Workspace add-on that simplifies the process of transforming your Google Sheets™ documents into JSON files. With Sheet to JSON, you no longer have to download individual sheets as CSVs and compile them later. Instead, you can quickly and conveniently export any Google Sheet™ document as a JSON file – with several different types of JSON to choose from and the option to define a custom JSON from Google Sheets™ workbook cells. 
Once you’ve exported your document, you can view the JSON directly or export and store it as a separate file in the same location as your original file. 

Free version restrictions:
 * Process only 25 rows of sheet