I personally have 2 steeping methods that I use regularly and to excellent effect.
Method 1: Ultrasonic cleaner (if you own one).
Decant the juice into a glass vessel (very NB) and place in the ultrasonic cleaner (covered or uncovered doesn't really matter, but I tend to do mine covered for safety's sake. Fill the cleaner with cold/room temp tap water. Set the cleaner to a 30 minute cycle.
When the cycle begins i normally read the temperature at being between 10ºC and 22ºC depending on the season and weather. After running a 30 minute cycle I take the temperature again. Again depending on the season and weather one may observe anything from a 15ºC to 25º rise in temperature.
The ultrasonic vibrations (42000 pulses per minute) do 2 things. Firstly they mix the juices various components together faster that you could even imagine. Secondly, the intensity of the pulses actually causes friction between the water molecules, heating the water up. (I have not tested whether or not one could could actually boil water this way, but have managed to bring the temperature up to 70ºC at one point just to see. I'm pretty sure based on those results that it would be possible.)
So the sweet spot is really aroung the mid 40's. Don't ever go higher than 50ºC just to be safe. Run as many cycles as you need to to achieve this temperature, then allow the juice to stand in the water until the water returns to its original temperature. Rinse and repeat as many times as you like.
I once did this to a juice 6 times cos I'd bought it at vape meet and had to add nic myself. It started out clear. By the end of the 6th cycle it was a deep orange!
Method 2: Your car
Put your juices in a tupperware or something. Must be preferably white plastic. Park your car somewhere in the sun, go shopping, have a coffee, go about your daily business. After a week it will be good and properly steeped and taste fantastic.
I personally prefer Method 1 cos it gives me complete control over the process, but that being said I rarely have the time to do it and as a result use Method 2 much, much more.
On the boiling side, exactly the same principle applied with a microwave, just the medium differs; being a radio wave instead of a mechanical wave.