Food safety
Can dogs eat cucumber?
Yes — fine in small amounts
Mostly water. A good hot-weather nibble.
How much
A few slices
Being honest about this
Dogs differ, and amount matters — a crumb of something rich is not the same as half a packet. Treats of any kind should stay under a tenth of what your dog eats in a day. If you're unsure, your vet would far rather take the call.