Millennials are no doubt a major economic player - 18 to 33 years old hold about 1.3 trillion dollars of spending power, according to a study by RBC Capital Markets.

That spending power has the ability to make or break restaurants, and restaurants are watching trends with trepidation. Over the past seven years, millennials have slowed restaurant spending by 21 percent.

What draws millennials to restaurants is digital savvy and high-quality ingredients. Places like Panera and Chipotle lead with fresh ingredients, made-to-order food in a fast-casual environment.

Starbucks leads the curve with a smartphone app that replaces rewards cards, including the ability to pay through the app.

Meanwhile, traditional fast food like McDonald's are suffering. Despite attempts to court younger customers with healthier items like yogurt, salad and soups, McDonald's has posted a fifth consecutive month of declining profits.

Read More:

• How Millennials Will Dictate The Future Of Fast Food (Forbes)
• Are McDonald's, Wendy's and Pizza Hut stuck in the past? (MarketWatch)