Marylin, To drain something that you cannot tip over or put a hole in, try using a cloth siphon or cloth wick or strip. Use something absorbent like cotton, wet the whole thing and insert the end into the soil of the container. The other end must be lower than the level you want to drain. Takes a while and you may have to play with thickness, length, etc. to get it working effectively. You should see water dripping from the lower end of the strip once it is going OK.
Other than that, one other approach is just to soak up excess water with towels, ring them out, then repeat until most of the water is gone. A permanent wick is a permanent solution, if you can find a way to route one into the container and assure it gets completely wet when drainage is needed.
