Amazon has a Buy $20 Get $7 Off Soft Drinks promotion with free shipping on $35+ or with Prime with coupon code CSDBXGY. 

A number of the 12oz, 12-packs (Root Beer / Zero Sugar Ginger Ale / Dr Pepper / Sunkist Orange Soda / 7UP Cherry / Squirt Soda) are $4.98. Add 5 to cart (mix and match) for $24.90 - $7 promo = $17.90. Drops the price per 12 pack to $3.58 each. 

There's also 12-pack 16oz Mountain Dew Kickstart options available for $15. Add two to cart for $30 - $7 = $23 (or about 96 cents per can).