Never use any kind of liquid to clean a toaster, let along clean it while its plugged in. It’s VERY important to clean only when its unplugged. If there’s a tray inside which collects crumbs, go ahead and clean that first. Afterwards, go ahead and flip the toaster upside down and shake out any remaining crumbs. Exterior can simply be wiped down by a damp rag, or even polished up if you have any stainless steel or chrome finish.