Most people prefer smoothies—which turn fruits into irresistibly silky beverages—over their competitor, roughies, which transform fruits into hardened criminals. Go the smooth route with today's Groupon: for $6, you get $12 worth of smoothies at Smoothie King on Union Avenue.

Smoothie King's blended-brew tycoon, Steve Kuhnau, reigns over more than 600 locations, mixing up a menu of nutritious sips since the 1960s. A waist-conscious trio of papaya, bananas, and strawberries casts a slender shadow as it leaps into the Caribbean Way, a drink that can be further slenderized by removing its turbinado sweetener or by enrolling it in boot camp ($4.49/20 oz.; $6.49/32 oz.; $7.99/44 oz.). Customers can slurp on the Angel Food's heavenly swirl of low-fat banana, strawberry, and vanilla flavors, contained within a frosty fusion that's less than 400 calories. The coffee smoothie mocha revivifies sluggish souls with a velvety java elixir that packs an energizing punch powerful enough to transform any sleepyhead into a fast-talking auctioneer. Meanwhile, whey and egg whites team up in the Gladiator, a low-carb, high-protein meal replacement designed to beef up physiques with a choice of two fruits.