A 10-stamp card with a free drink suits the price point and the frequency. Put a pin on the gym next door as well as your own door, so the card appears on the lock screen when a member finishes a class.
A membership card for the regulars, a set price a month for a daily juice, takes the card from a habit to a subscription and is visible as Active to staff at a glance.
Build your card in fifteen minutes
Bring your logo and the price of the drink you give away.