My mom always makes homemade juice (Polish called "kompot") in the summer and it is so good, warm or cold.
When I plan to make homemade juice, a week beforehand I save empty juice bottles to use as storage for the homemade juice.
Use the same method for other fruit combinations; other additions that taste great are pears, plums, peaches, raspberries and blueberries..
Fill half of stock pot with lid. (You can also use a smaller pot, just use less fruit and sugar.)
Wash all fruit. Slice tops off strawberries. Cut strawberries in half and put in pot. If some strawberries are small, just put them in whole.
Peel mango, slice into quarters and add to pot. Cut orange into slices; add about 3 slices (with peel on) to the pot. Stir. Cover and bring to a slow boil.
Add sugar. Cover and lower to a simmer. Let simmer for about 25 minutes, stirring occasionally.
Add mint leaves (optional! I just have a bunch in my garden so I added them).
At this point, strawberries should be losing their color and the mango should be pretty shredded and dissolved looking. Taste the juice. Add sugar if its too tart. Add water if its too sweet. Cover and simmer 15 more minutes.
Take pot off stove and put in a place where it can cool. Let cool mostly before serving, although some like to drink this warm / hot.
If you like pulp, the pulp will be resting at the bottom. I do like to save the pulp for my juice, but if you don't, use a strainer to separate juice from pulp.
Store juice in fridge in an empty juice bottle or airtight pitcher. It will be good for about 5-7 days in the fridge.