Leaking juice bottles

I purchased 2 juice bottles for my sons for school. The next morning I put juice in for school and both bottles leaked and I will not even attempt a zip lock to prevent the juice from spilling out in their school bags. I asked my mother in law to go back to exchange the bottles for other bottles and the manager said no as the bottles have been used! I'm unhappy with the service as we make use of the spar on a regular basis and they not even exchange bottles that leak. I expected something different but was sadly mistaken