Dakota Johnson dropped a shocking bombshell — about how addicted she was to Celsius. In a video seen by RadarOnline.com, the famous offspring, 34, admitted she nearly “overdosed” on the energy drink after she failed to realize it was packed with caffeine. “I discovered Celsius on [the first day] of filming the short and I didn’t know that it was Red Bull,” she told Variety about how she was quenching her thirst while shooting the movie Loser Baby. Johnson, who directed the project, said she “thought it was just vitamins” and considered it a “natural drink” filled with “B12 and vitamin A” to ke…