chocolate-milk alternative
Refers to a "just as bad or worse" substitution-product/activity employed to supposedly "fill the void" created by a discontinued unhealthy habit --- the idea here is that while the milk itself may indeed be low-fat, the added calorie-rich and sugary-sweet chocolate has far more fattening ingredients than just the cream in full-fat milk could possibly have contained, and so the person will likely gain even more weight than ever.
Three classic --- and very tragic --- examples of a "chocolate-milk alternative" would be a substance-abuse recovery-program's giving a dry-drunk lots of high-sugar foods in place of alcohol, someone's switching to compulsive shopping in place of gambling, or a person's becoming harshly-snappy and irritably-demanding after giving up cigarettes.