Technically you could put any text you want in it. Most of the ones people are posting today, including me, are with ecash tokens. I just the CoinOS.io wallet to make them. Send a few sats to the wallet, and then hit the send button and select mint ecash. If you make one and no one redeems it, you can redeem it yourself back into your wallet. Cashu.me is another good ecash wallet.