The following is a list of drs that are known, suspected, or rumored to exist

Dr. Best 76
Dr Cheer Wades Super Market (Rich Foods)
Dublin, VA;
IGA grocery
North Carolina;
Community Pride
Richmond, VA
only in 2L?
Dr Choice Farmer Jack (America's Choice)
Harrisonburg, VA
No relation to Best Choice's Dr. Choice
Dr Diablo Shasta Beverages, Inc. From the 1980s. An early Dr. Shasta?
Dr Flag Grand Street
New York, NY
Dr Foots Bavaria Beer Company
I'm suspicious that this is not a soft drink.
Dr Foots / Foots c. 1970. Named after Woodrow Wilson "Foots" Clements, CEO and president of the Dr Pepper Bottling co. in 1970. Changed the name to Foots under pressure from DP.
Dr. Gibb's Gibson's Original Soda
Dr Lariat Roswell, NM; Jaurez, Mexico; Albertson's in Prescott, Arizona
Dr. Lightning Wal-mart (Sam's Choice) Wal-mart's interim drink between Southern Lightning and Dr Thunder
Dr Ozark Branson, MO
Dr. Perfect Boston, MA? A dollar-store version, different from Bi-Lo's Dr Perfect
Dr. Pip Atlantic Beach, NC Fountain only?
Dr Polar Charlottesvile, VA
Dr. Rescue
Dr Rock Rock Creek
Washington, D.C.
2-L bottled by Canada Dry Potomac
Dr. Select Vons Companies, Inc.
San Diego, CA
Dr. Slots
Dr Smith's Smith's Grocery
an older version of Dr Wild?
Dr South
Dr Sparks
Dr Sweet ALDI discontinued?
Dr. Sweet Wildwood
Dr. Swett's O-So circa 1950. In 24 oz. bottles. I'm not sure if this is really an imitation, or if it is just the name. See Beverage World, July 15, 1999, pg. 12.
Dr Taste
Dr Up Worldwide Beverage Co.
Atlanta, GA; Hickory, NC
Dr. West Southwest Supermarkets
Phoenix, AZ
Southwest Filed for Chapter 11 and was bought by Bashas'. Bashas' supposedly turned all 32 stores into Food City, so this Dr. West may very well be no longer distributed.
Dr Whoa! Schmidt's
Dr. X
Dr Zeppa Store 24
Providence, RI; Boston, MA
Only in 2L?
Dr. Zipp Holiday Company
Peppo Coca-Cola