Schweppes' Solo is a little more sweet, and less sour, in all, they have the best compo of all lemonades.
The cheapest liquid on store: store-brand bottled water, IDR 3,000 (USD 0.35) for 600 ml.
In the whole town (drinkable): street-side hot tea in glass, IDR 1,500 (USD 0.18) in a 500 ml glass.