This is a demonstration model for explaining why a stream of water is attracted to a charged balloon (or similar). Students can try to find the answer themselves by sliding around the charges. 

The straight stream (a) is used to get an initial state without a charged balloon nearby; the charged ions are evenly distributed.

When the (here negatively) charged balloon etc. is close, electrostatic induction occurs, positive ions are attracted, negative ones are repelled, and the positively charged stream section bends towards the negative charge (b).

If you try the same with a stream of separate drops, the charges can not separate that far, the negative charges at the back side are nearly as much repelled as the positively charged front of the droplet is attracted (note that the sizes of balloon and droplets are not at all to scale, so the electrical field from the balloon is much less inhomogeneous and both forces are very close in reality) and the net force is negligible and insufficient for noticeable deflection (c).

I meanwhile added a bigger charge disk/coin to represent the straw/balloon instead of the gray disk with 3  charges inside shown in the image.

Printing:

0.2mm layer height. The ions are supposed to get a color change for the topmost layer (MMU not required). 
You can probably place two sets of water steams & droplets on one plate when shuffling them around a bit, depending on your printer.

Notes on the effect: 

• It is often taught that the water stream's deflection is due to the polar nature of water molecules - but this explanation, even found in chemistry textbooks, is wrong. You can try to disprove it yourself: Use a relatively thin charged object like a plastic straw and try to deflect a stream of distinct droplets instead of a continuous stream (be sure to hold the straw quite a bit below the point where the stream separates into droplets, so the electrical field is too weak for relevant electrostatic induction at that point) - the droplets will not be deflected.
• This even applies to distilled/pure water, since even that has ions (self-ionization of water, H+/H3O+ and OH-, 10^-7 moles/liter) and thus has a very low, but non-zero conductivity, enough to move the minute amount of charges required for the effect.
• Here's a scientific article about that topic: Ziaei-Moayyed, M.; Goodman, E.; Williams, P.: "Electrical Deflection of Polar Liquid Streams: A Misunderstood Demonstration",  J. Chem. Educ. 2000, 77 (11), 1520, https://doi.org/10.1021/ed077p1520
• Since the full article isn't publicly available (you might find it by searching the internet though), here's a video by Veritasium at time 3:47.

Notes from a teacher who used this model to let students discover the explanation:

• The students worked in small groups of 3-4. 
• It was established in lessons before (on multiple occasions) that water is conductive.
• Electrostatic induction was also already covered using the example of metals.
• Some groups didn't separate the ions at first and needed a bit of hinting.
• In the following discussion the students came up themselves with the issue that the stream of water moves downward and also will negative ions. However the attracted positive ions will stay longer near the negatively charged balloon/straw etc than the repelled negative ions, so the section close to it still is positively charged and thus attracted.
• The students then usually can explain what happens in case of a positively charged object near the water stream.