Some thoughts:
1. Distilled water will work; don't worry about the juice.
2. Double check your hygrometer.
3. Be patient; put the sponge or shotglass or both in there longer.
4. If this doesn't work, the humi may not have a good seal. To check, put the sponge in the humi, put in the hygrometer, and put the whole humi in a kitchen trash bag overnight. The next morning, check the hygrometer; it should be 70% or higher. Take the humidifier out of the trash bag, but leave the sponge inside and see whether the humidity drops by nighttime or the next morning. If it does, the seal is probably leaky. If not, you've got the humidity up where you want it.
Good luck.