Birch sap is my first thought, but I might get tired of the sweet. Some kind of tea then, maybe rooibos. It's sweet or savoury as the occasion demands.
TIL that's a thing you have to worry about. It has 52% of your daily value per 100 grams, according to Wikipedia. It looks like we're pretty well adapted to clear excess amounts out, though, so maybe it's fine?