Squeeze-it water enhancer. There’s several hundred different flavors, you can add however much you want at that time, so you can make it stronger or weaker as the mood hits you. Most are typically 0 cal, but IIRC there are some that have no sweetener at all. Search for “water enhancer”, but here are some examples. I’ll also make them go further by adding them to some iced tea, so you can make an Arnold Palmer. Variety is the spice of life.