Every account is different and what works for one may not work for another. Here are some ways that multiple coupons have been issued to contacts when they join. 

1) Create one campaign that a contact can join, that sends them 4 interactive messages with each linked to a different coupon. 
  • Pro = easy 
  • Con = Sends 4+ messages and offers can be difficult to change if linked in the scheduled log

2) Create one campaign that a contact can join, that sends them 1 interactive message with a linked coupon or mobile webpage configured with multiple buttons or links they can use to select coupons to be issued to them. This process was covered in a 2019 webinar. See - WEBINAR: Chamber "Shop Local" Program Set-Up 11/06/2019
  • Pro = contact chooses what they want, which helps with analytics
  • Con = more work to set-up

3) Use APIs that process Post Notifications for SMS Keyword opt-ins to a Zapier webhook that triggers Issue Coupon API to issue the contact the desired coupons without sending a text message. 
  • Pro = saves messages
  • Con = Requires 3rd party processing, and additional instructions for the consumer to see that their offers are available

Then there are the more obvious...
4) Create four different campaigns consumers must join in order to get 1 coupon from each campaign.
  • Con = Too many steps for text in

5) Create trigger messages to issue the coupons to new opt-ins. 
  • Pro = Better alternative to option 1 than using 4 interactives because the messages and offers are easier to revise