Voltage depends on the chemistry. It's what is known as an intrinsic property, independent of scale and only dependent on the thermodynamics.
Current (mA) and capacity (mA-hours or mAH) depend on the volumes, surface areas, cleanliness of the electrodes, and so on. Current is essentially a measure of how fast the reaction is occurring. This is called an extrinsic property, and can be very hard to predict because of all the variables. Current will usually start at one level and decrease as your cell runs down - just like a battery - but also because of fouling of the electrodes, reducing the surface area.
Copper and Zinc in a solution can get you up to 1.1 volts if not loaded. With only 50 ml and simple strips of metal, meaning only a sq. few cm of each metal, I would not expect you to be able to get more than a few hundred microamps, and that would probably also mean loading down the voltage considerably.
You could flash an LED with it if you use a very efficient voltage up-converter.