The credit-card rewards wars are heating up. A growing number of credit-card issuers are rolling out rewards programs that promise to give card users more cash back for their purchases.

The latest addition is Citizens Financial’s newest credit card, announced on Wednesday, that offers cardholders 1.5% back on every purchase. The Cash Back Plus World MasterCard doesn’t cap the dollar amount that borrowers can get through this rewards program, and it allows them to get up to 1.8% cash back in total if they use the card at least...