HTTP Google Sheets API v4 how to access without OAuth 2.0?

All Google APIs require that you create a project on Google developer console and identify yourself and your application, even to access public data. Since you have set the sheet to public you can just go to google developer console and create a public api key remember to active the google sheets api. Then just add key=[YourKey] as a parameter on your request.

Update Dev console:

Create project and get key:

Google developer console -> create a project -> credentials drop down -> API Key

Enable it:

Google developer console -> library find sheets enable it.

Update:

{ "error": { "code": 403, "message": "The request is missing a valid API key.", "status": "PERMISSION_DENIED" } }

Means that you have not identified yourself to Google. In 2015 Google Start to require that we identify ourselves you cant just use a Google API without telling google who you are. You do that by creating a project on [Google developer console1. Create an API key and use that API key in all of your requests. This only works with Public data.

https://sheets.googleapis.com/v4/spreadsheets/1F6jh6756xNDlDYIvZm_3TrXb59EFEFHGEC7jdWz-Nx0/values/Sheet1!A1:A3?key=YOurKEY

Note: With private user data you would need to use OAuth and use either access_token=your token or set the header

Authorization: Bearer ya29.GlvaBLjrTdsSuSllr3u2nAiC-BOsjvIOE1x5afU3xiafB-FTOdLWDtfabuIMGF1rId5BsZxiTXxrx7VDEtxww4Q1uvW9zRndkfm3I2LZnT1HK2nTWzX_6oXu-NAG.

An access token is not the same as a API Key.

If you don't want to mess with OAuth2, maybe the simpler solution is to use third-party soft. https://sheetdb.io allows you to work with Google spreadsheets and does OAuth2 for you. Additionally, the API is simpler than Google, check out the docs here: https://docs.sheetdb.io