This DIY is super easy and fast (bonus: it's also environmentally friendly!)

Things you'll need:

Solar panel (I used a 3V / 250mA one)
An Eclipse mint tin (or whatever you like)
Some wires
Drill
2.5mm male jack
2.5mm female plug
DC to DC Boosting Circuit with USB
1N4148 Diode
Electrical tape
Hot-glue
Soldering iron
Solder

If your solar panel is more than 5V then you need a step-down circuit. If not, a step-up one (to 5V) is fine.

Step 1: The Solar Panel

I’m using the same solar panel from my Solar USB Charger project, so it’s already wired with a 2.5mm male jack. You can wire the panel directly to the circuit, but I prefer having a DC connector because I can use it to charge my phone, my phone charger AND my rechargeable batteries.

If you have not done so:

Solder the positive wire to the longer leg of the 2.5mm male jack and the negative wire on the other.

Step 2: More Soldering

Place the plug with the empty side facing down. The left tab is negative and the middle one is positive.

Solder the negative side of the circuit to the left tab, and the 1N4148 diode to the middle tab. Remember that the black side of the diode should be facing away from the tab. Hook it up to the positive side of the circuit with a wire.