I wasn't aware that fish sauce included any kind of sugar. Of the two I've got right now, one (Squid Brand) lists anchovy extract, water, salt, and MSG
; the other one lost its label years ago, so I don't know, but I doubt it has any kind of sugar.
Trachang brand shrimp paste is just shrimp and salt, but yes, the shrimp are fermented and quite pungent. Nothing like dried shrimp.