Infants are born with some basic taste preferences. In one research study, babies would suck faster and stronger for sweet liquids than bitter, sour, salty, or neutral (water) solutions. Also, sweet tastes tend to reduce crying and lead to contented facial expressions, whereas bitter solutions tend to elicit expressions of disgust.
Crook, C. (1987). Taste and olfaction. In Salapatek, P., & and Cohen, L. (Eds.), Handbook of infant perception. Orlando, FL: Academic Press.
Steiner, J. E. (1974). Innate, discriminative human facial expressions to taste and smell stimulation. Annals of the New York Academy of Sciences, 237, 229