The main reason many people water orchids with ice is to prevent over-watering. Orchids are susceptible to contracting diseases if they are left too wet, so this method can be helpful in gauging how much water an orchid should have.
Typically, three ice cubes equal about 1/4 cup of water, the ideal amount of water for an orchid, according to SFGate Home Guides. The easiest way to water an orchid with ice cubes is by placing a few ice cubes away from the main stem of the orchid and letting them melt. Drain any excess water off the plant. If too much water remains, try reducing the number of ice cubes.