You can give a very small amount of cranberry juice to your dog though this is not likely to help kidney dysfunction. Has kidney disease been documented? Blood work and a urinalysis needs to be run to determine if kidney problems exist, if so how severe, and to rule out an underlying urinary or kidney infection. Treatment is aimed at diet change to support the kidneys, fluid therapy as appropriate, and electrolyte supplementation and supportive care. Talk to your veterinarian about more effective treatments of kidney disease than cranberry juice.