Even in Brazil, the land of a thousand fruits, it's not practicable or even possible to have juice made from fresh fruits at all times and in all places. Fruits have seasons (even if the tropics themselves don't), and there are times when a particular fresh fruit is just not available.
Unfortunately, most prepared fruit juices in Brazil, the type you buy in the supermarket and store in the refrigerator, are highly processed and contain huge quantities of sugar. Even the orange juice that comes in a carton is sweetened!
There is a solution to this problem, however, and one which I wish would be adopted outside Brazil. The freezer section of all supermarkets has a selection of frozen fruit pulp, in a variety of flavors, which can easily be turned into delicious juice at home. The pulp is generally sold in units of 100 gr. To make juice, all one needs is a blender. Combine one package of pulp plus 400 ml. of water in a blender, blend at high speed, and you instantly have about 500 ml. of icy -cold, flavorful juice.
Pulp sold this way is pure fruit pulp, pasteurized, without preservatives or added sugar. Naturally, depending on the fruit, some sugar might have to be added to make the juice palatable, but the amount of sugar can be controlled depending on one's taste and/or dietary restrictions.
The variety of pulps available is enormous. Checking on the website of one of the major producers of these pulps, they list 13 varieties available pineapple (abacaxi), acerola, açaí, cacau, cashew (caju), cupuaçu, guava (goiaba), soursop (graviola), papaya (mamão), mango (manga), passion fruit (maracujá), strawberry (morango) and grape (uva).