Translate grammar sentences

One of the low-fun activities for me is the translation of sentences from L1 to L2. Some exams still have this tasks and some students still choose exams that have it.  Of course they are beneficial though. Khmmmm...
Suppose your students are to translate a couple of sentences that are examples of a certain grammar points.  You can post these on Facebook, you can assign two or three sentences to one student. After having translated them peers can correct or comment on each other's sentences.
Variation:

They will use Google Translate, it will give them sentences with errors. Why don't they correct them?

You can also give them google-translated sentences with errors, they would have to correct them and find out the original L1 sentence.

Translate and translate ...

The other day one of my students asked me to help him with a test-prep project.
They were doing -ed/-ing adjectives. 
They did the unit of a relevant grammar-in-use book.
Their teacher told them they were to be tested on the sentences in a couple of days. The test was translation from L1 to L2. This is very challenging as the subject of the test is not only -ed/-ing adjectives but a range of other points (other grammar, vocabulary, etc.)

On the other hand it was not just rote learning 10 sentences or so, there were about 70-80 sentences!!!

It was not a real option to write them each in two languages by one person to be studied later.

The number of learners in his group is 16. If they create a flash card set collaboratively, quizlet.com for example.  5 sentences (L1, L2) per person is quite manageable. So each student writes 5 virtual flashcards in collaboratively created virtual flashcard set (they may peer-correct it and the teacher can have a say too).
Now there’s nothing else to do but have a flashcard contest. The scores can be posted on Facebook, the winner may win a ..... something.