Wrong sentence:

Minta coba makan pure ini
Minta silakan makan pure ini

Please try eat this puree. 

Please (when asking for help/bargaining)

Please usually meaning : silakan, tolong, mohon. 

Ask and request usually meaning : minta.

which is the wrong sentence?

Minta coba makan pure ini (X) ---> Rough translation in English is "I ask you to try this puree", however this doesn't sound natural.

Silakan coba makan pure ini (✓) ---> This sounds more natural to native ears, but we usually remove "makan" in this context, so we say "Silakan makan/coba puree ini", pick either makan or coba to avoid redudancy.

Minta silakan makan pure ini (X) ---> The sentence composition is not right here. It should be like in English "Kindly (adverb) try (verb) this puree (object)" or "Silakan makan/coba puree ini"


Hope that helps.

Minta= ask
Silahkan= please

For informal conversation, you can say=
Boleh saya minta coba makan pure ini?

But if you only say 'minta coba makan pure ini' it sounds like an uncomplete sentences

The second one is correct you can say that.

and the last one, 
Minta silahkan coba makan pure ini. 
You can't say that.. Sounds weird.
Silahkan usually we put on the first sentences.

You can say "please ask her to try eating pure"
"Silahkan minta dia untuk coba makan pure"