Pour 2 tbsp. of cooking oil into the bottom of the dishwasher, then pour table salt liberally over the suds. This helps break down the surface tension of the bubbles.
Add ice to the dishwasher to drop the temperature of the water and break down more suds.
Engage the "Drain" cycle" in your washer, or use a wet/dry vacuum to remove suds and water from the bottom of the unit. Roll out and remove the bottom rack to get the most access to the bottom of the dishwasher.
Wipe up any residual suds or soap from the bottom of the unit.
Turn the washer on a normal cycle and monitor the suds. Repeat the salt and ice application as needed. For stubborn foam in the dishwasher, add a few squirts of defoaming product normally used in pools and spas or a capful of liquid fabric softener to the washer, and run it as normal.