the way i got this is by choosing the endless run button and then it asks you if you would like to send a challenge to a friend. At this time you want to check 25 different friends or if you have less than 25 friends just send 25 challenges among your playthroughs of endless runs. then after sending the challenges try and run as far as you can or just die as soon as you're able to and then a screen will pop up saying that your challenges are being sent to your friends and achievement should pop! any questions? just leave a comment :D
martijn tigurr got this another way also! " I got the achievement by challenging only 10 friends and then running for as long as I could and then exiting the game with Alt-F4" so if you guys wanna try this way also go ahead!