SAN FRANCISCO — Sweet Nothings, a maker of organic, plant-based smoothies, is launching its first children’s products this month. The debut of squeezable smoothies in Whole Foods Market stores across the country is one of several recent milestones for the San Francisco-based startup.

Packaged in “kid-friendly” tubes, the squeezable smoothies are formulated with organic fruits, vegetables and chia seeds. Flavors include pineapple spinach, mango carrot and strawberry beet. The products are merchandised near bagged frozen fruit, which “speaks to the versatility of the occasion” and the nutrient-dense ingredients, said Jake Kneller, co-founder and chief executive officer.

“We’ve done focus groups with parents and learned more about when a product like this could fit into their lives and their kids’ lives,” Mr. Kneller said. “It wasn’t something that they thought of replacing a popsicle full of cane sugar and fruit juice. It was, ‘This could replace a yogurt tube or string cheese or applesauce.’ … You would never put a dessert in the frozen fruit category, so there’s a lot of credibility and a lot of flexibility that comes with that placement.”

The products, which are free from the top eight allergens and produced in a dedicated facility, also will be available to purchase through online retailer Thrive Market.

“Parents who want their kids to eat more fruits and veggies, or they’re looking to stay away from dairy for allergies or other reasons, can throw this in a lunchbox instead of that yogurt tube or string cheese, and the kid loves it,” Mr. Kneller said. “They think they’re getting dessert. It’s sweet, flavorful, a little tangy. And the parent obviously knows that it’s a truly healthy option.”

The brand’s flagship line of single-serve, spoonable smoothies, which are plant-based with no added sugar, is rolling out to more retail locations. Following a successful test, the products will be available in select Kroger divisions this summer, Mr. Kneller said. Sweet Nothings spoonable smoothies contain a blend of fruits, vegetables, nuts and seeds. Flavors include strawberry, dark chocolate, peanut butter, tropical greens, blueberry and mango.

Co-founder Beth Porter, a longtime entrepreneur with a passion for health and wellness, developed the initial recipes several years ago in her home kitchen following her young daughter’s decision to adopt a vegetarian diet. The products, packaged in grab-and-go cups containing a small spoon, were designed to deliver the benefits of a homemade smoothie without preparation or clean-up.

Rebranded packaging is rolling out soon, designed with vibrant hues and clearer communication to stand out on shelf. Distribution gains and the addition of the children’s offerings bring the brand’s retail footprint to 2,500 doors, Mr. Kneller said.

Last fall marked the introduction of shelf-stable snack bites featuring fruit, nuts, oats and flax seeds, which are now sold on Amazon.com.