I drill a hole in the bottom of the cups & bowls with a diamond hole saw. You can get a set of 9 on amazon for under $8 with free shipping -
https://www.amazon.com/dp/B00S2WKQAC/
Just put water in the bottom of the container to keep the bit cool and drill away. The bits are a little hard to start because they don't have a center bit but I just tilt the bit side ways until I get a groove start and then go vertical to finish it off.
Good luck,
Dan