How to send empty message in telegram bot?

You can't send empty message now, it was a bug for zero-width space ​ and RTL (Right-to-Left) control character, but it can't send along now.

You can try Alt + 0173 in the Numpad. Press and hold the Alt key and click on 0 then 1 then 7 then 3.

I don't think there is a way to do what you want.

Consider this:

https://api.telegram.org/botYOURTOKEN/sendMessage?chat_id=ID&text=

Since even space is not accepted, there are no other characters that can be encoded to represent "nothingness".