Tap and hold on the icon of a pet you own in the furnishing menu. Select the red button labeled "Dismantle" of a pet you're willing to sacrifice. On the next screen, tap and hold the button at the bottom of your screen until a success page pops up. You'll have earned: several of each colored ug material and some pieces of meat. To upgrade your pet, select the blue "upgrade" button instead of the dismantle button. Follow the same process. Dismantling furniture is permanent. The only way to get meat (or other slot-specific material) is to dismantle another pet (or other specific slot furn for other material). You cannot trade any slot-specific ug material, only the red/yellow/blue stuff.