I would like to know the meaning of this, thank you:

Gözyaşının akmasına bazen bir soğan değil, bir hıyar da neden olabilir!

 sometimes  it is not an onion  for tears to flow ,a cucumber can also be the  cause 

´´hıyar´´ used in different meanings  

1.hıyar :cucumber

2.hıyar :stupid/blockhead (rarely or never used for females)

it is not a polite word so when we talk about a cucumber(vegetable) we need to use ´´salatalık´´ =cucumber (vegetable)

ex: hıyar yemeyi severim : ı like to eat cucumber

     ne hıyar bir adamsın :what a stupid/blockhead man you are.

" hıyar" in slang language might be used for people who are insane or whose behaviour is not so kind or impolite somehow .....

so then  translation is :

it is not an onion that cases the tears come down your eyes ,but a man (called hıyar)might be the reason why the tears are coming down your eyes ...

Ps:cucumber has got nothing to do here

b.rgds/ally

I didn`t actually think a cucumber could make your eyes water unless of course its a big one and you get poked in the eye with it

a couple of changes for better English

Wow, thank you all guys for your helpful explanations