Can I ask delivery-app customers to order directly next time?

It depends on the app. Deliveroo and Zomato restrict your own branding on their orders. New York City lets restaurants include menus or coupons. Uber Eats customers can opt in to hear from you.

• Deliveroo: flyers or branding that promote your own channel in or on its order bags count as not acting in good faith.
• Zomato: no third-party branding on packaging of Zomato orders. Customer data is for fulfilling the order, not unsolicited marketing, unless the customer opts in.
• New York City: a delivery platform must let a restaurant include menus, coupons or other printed marketing with any online order.
• Uber Eats: a customer can choose to share their name and email with you. You may send offers only after they opt in.