I have given my kid herbal teas (first fennel seed for her colic, then chamomilla, peppermint, "winter" mixes against coughing, ...) since she was 4 months old, no sugar. She's used to it and prefers it to juice. There is no risk involved in giving herbal tea at all (unless you choose herbs of dubious origin of course). I have always used big organic brands. If you are not giving your children excessive amounts of sweets or sugar, they will not ask for sweeteners in the tea. That is my experience, anyway. It's a question of habit.