Glytactin RTD LITE Oral Supplement Coffee Mocha Flavor Liquid 251 ml CartonOral Supplement Glytactin RTD LITE Coffee Mocha Flavor Liquid 8. 5 oz. Carton Glytactin RTD LITE Coffee Mocha is the lowest calorie, lowest Phe GMP based ready to drink medical food for the dietary management of PKU. All Glytactin RTD medical foods contain Glytactin, the advanced formulation of whole protein glycomacropeptide (GMP) and essential amino acids, and with lower Phe. 8. 5 ounce carton.