Who doesn’t love free things—especially when that free thing is coffee? Thanks to a new sustainability initiative at Starbucks, you can score free coffee when you bring in your own cup.

Starting on Earth Day (April 22) Starbucks is introducing a new rewards perk that’ll help you earn more points toward a free drink every time you bring in your own reusable cup.

To take advantage of the new deal, you’ll need to be a member of the Starbucks Rewards program, which allows members to collect stars that act as points. As you receive more stars, you’ll also receive the following bonuses and deals:

• 25 Stars: A free drink customization.
• 50 Stars: A free brewed hot coffee, bakery item, or hot tea
• 150 Stars: A free handcrafted drink, hot breakfast, or parfait
• 200 Stars: A free lunch sandwich or protein box
• 400 Stars: Free select merchandise or at-home coffee

With the new promotion, each time you bring in a clean, reusable cup (nope, it doesn’t have to be from the brand), you’ll get an additional 25 stars and 10 cents off your purchase. As you continue to bring in your reusable cup, you’ll also continue to build up rewards until you can score a free drink at 150 stars (or keep going for even bigger benefits).

The initiative is part of Starbucks’ plan to reduce waste by 50% by 2030, and in the process, it can help you become more sustainable, as well. On April 22, when the new reward system starts, all Starbucks merchandise will be 30% off, making it the perfect time to snag that reusable cup.

If you hit your local Starbucks every day, this new rewards perk can score you a free drink. So, if you don’t normally use it, it’s time to dig that travel mug out of the cabinet.