HY is nothing but denotes an affirmative response to a question, there exists no other way of interpreting this acronym.
To understand how to use HY on Snapchat, follow these steps:
1. Open your Snapchat account and take a photo using Snap's camera.
2. Go to the right side of the panel and select the "Stickers" button.
3. Use the search feature to find "Hell Yea" and browse through the stickers and Bitmojis related to the acronym.
4. Choose the one you like and add it to your snap.