How does Lindsay Lohan keep up with her busy schedule of travel and partying? Must be the Red Bull!

LiLo was snapped stepping out of the Ritz-Carlton in Midtown Manhattan yesterday -- rockin' a can of the Bull -- but minus her most recent fashion accessory -- hunky boy toy Calum Best.

The serial dater and her man of the moment returned to the U.S. after a wet and wild Bahamas getaway -- where they were spotted swappin' spit in the waves.