What lube should I use with a clitoral suction toy?

Water-based lube is the safest choice for most suction toys, especially silicone ones, since silicone lube can damage some silicone surfaces. You only need a drop on the rim of the nozzle to improve the seal and reduce friction. Avoid oil-based products unless the manufacturer says they're fine. Too much lube can make the nozzle slide around, so start small.